Magnetoresistance effect element

ABSTRACT

It is an object of the present invention to provide a magnetoresistance effect element which has a film with a spin valve structure or an artificial lattice film having good soft magnetic characteristics, and which can be applied to a high-sensitivity magnetic head. The present invention provides a magnetoresistance effect element including a stacked film formed on a substrate by sequentially stacking a ferromagnetic film containing as its main constituents at least one elements selected from the group consisting of Co, Fe, and Ni, a nonmagnetic film, and the ferromagnetic film, wherein the two ferromagnetic films are not coupled with each other, and the closest packed plane of each ferromagnetic film is oriented in a direction perpendicular to the film surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetoresistance effect element foruse in a magnetic head and the like.

2. Description of the Related Art

Generally, to read out information recorded in a magnetic recordingmedium, a reading magnetic head with a coil is moved relative to therecording medium, and a voltage induced in the coil by electromagneticinduction generated upon the movement is detected. A method using amagnetoresistance effect head to read out information is also known[IEEE MAG-7, 150 (1971)]. This magnetoresistance effect head makes useof a phenomenon in which the electrical resistance of a certain kind ofa ferromagnetic substance changes according to the intensity of anexternal magnetic field, and is known as a high-sensitivity head for amagnetic recording medium. Recently, as magnetic recording media havebeen decreased in size and increased in capacity, the relative velocitybetween a reading magnetic head and a magnetic recording medium duringinformation reading has decreased. Therefore, development of amagnetoresistance effect head capable of extracting a high output evenat a low relative velocity has been desired increasingly.

Conventionally, an NiFe alloy (to be abbreviated as a permalloyhereinafter) has been used in a portion (to be referred to as an MRelement hereinafter) of a magnetoresistance effect head in which theresistance changes in response to an external magnetic field. Thepermalloy, even one with good soft magnetic characteristics, has amaximum rate of change in magnetic resistance of about 3%, and thisvalue is too low to use the permalloy as the MR element for asmall-size, large-capacity magnetic recording medium. For this reason, ademand has arisen for an MR element material with a highly sensitivemagnetic resistance change.

In recent years, it has been confirmed that a multilayered film formedby alternately stacking ferromagnetic metal films and nonmagnetic metalfilms, such as Fe/Cr or Co/Cu, under certain conditions, i.e., aso-called artificial lattice film gives rise to a very large change inmagnetic resistance by using antiferromagnetic coupling between adjacentferromagnetic films, and a film which exhibits a maximum rate of changein magnetic resistance exceeding 100% has been reported [Phys. Rev.Lett., Vol. 61, 2472 (1988)] [Phys, Rev. Lett., Vol. 64, 2304 (1990)].

Another type of a structure has also been reported, in which althoughferromagnetic films do not experience antiferromagnetic coupling, anexchange bias is applied to one of two ferromagnetic films sandwiching anonmagnetic film by using some means other than antiferromagneticcoupling between adjacent ferromagnetic films, thereby locking themagnetization of the film, while the magnetization of the otherferromagnetic film is reversed by an external magnetic field. This formsa state in which the two ferromagnetic films are antiparallel to eachother on both the sides of the nonmagnetic film, realizing a largechange in magnetic resistance. This type is herein termed a spin valvestructure [Phys. Rev. B., Vol. 45806 (1992)] [J. Appl., Phys., Vol. 69,4774 (1991)].

In either of the artificial lattice film or the spin valve structure,the resistance change characteristics and the magnetic characteristicsof the multilayered film change largely in accordance with the type ofthe ferromagnetic film. For example, in a spin valve structure using Co,such as Co/Cu/Co/FeMn, a high resistance change rate of 8% results, butthe coercive force is as high as approximately 20 Oe, i.e., no good softmagnetic characteristics can be obtained. In contrast, in a spin valvestructure using the permalloy, such as NiFe/Cu/NiFe/FeMn, although agood value of 1 Oe or less has been reported as the coercive force, theresistance change rate is not so high, about 4% [J. Al. Phys., Vol. 69,4774 (1991)]. That is, the soft magnetic characteristics of the stackedfilm are good, but its resistance change rate decreases. Therefore,neither a constituent element nor a film structure of a stacked filmwhich satisfies both the soft magnetic characteristics and theresistance change rate has been reported yet.

In addition, the above two types of the films have the followingproblems.

The artificial lattice film has a higher resistance change rate ΔR/R(ignoring a magnetic field range) than that of the spin valve structure.However, a saturation magnetic field Hs of the artificial lattice filmis large because antiferromagnetic coupling is strong, so the filmsuffers poor soft magnetic characteristics. In addition, since thisRKKY-like antiferromagnetic coupling is sensitive to an interfacestructure, stable film formation is difficult to perform, anddeterioration with time readily takes place.

A film with the spin valve structure can achieve good soft magneticcharacteristics when an NiFe film is used as the ferromagnetic film.Since, however, the number of interfaces between the ferromagnetic filmsand the nonmagnetic film is two, the ΔR/R is lower than that of theartificial lattice film. Even if a stacked film is constituted byferromagnetlc, nonmagnetic, and antiferromagnetic films in order toincrease the number of interfaces, since the antiferromagnetic film witha high resistance is present in this stacked film, spin-dependentscattering is suppressed. Therefore, no increase in the ΔR/R can beexpected.

In addition, when a signal magnetic field is applied in the direction ofthe axis of hard magnetization of ferromagnetic films suitable for amagnetic head, the magnetization of only one of the ferromagnetic filmsis rotated. As shown in FIG. 1, therefore, the angle defined between themagnetization of a ferromagnetic film 2 on an antiferromagnetic film 1and the magnetization of a ferromagnetic film 4 on a nonmagnetic film 3can be changed to only about 90° by the application of the signalmagnetic field. Note that a change in the angle of up to 180° occurs inthe direction of the axis of easy magnetization. Consequently, the ΔR/Rdecreases to about half that in the axis of easy magnetization. Assume,for example, that the exchange bias magnetic field of the ferromagneticfilm 2 on the antiferromagnetic film 1 is weakened by some method tomake it possible to use the magnetization rotations of both theferromagnetic films 2 and 4. In this case, if the film thickness of thenonmagnetic film 3 is decreased to increase the resistance change rate,ferromagnetic coupling acts between the two ferromagnetic films.Therefore, the magnetizations between the two ferromagnetic films pointin the same direction when the signal magnetic field is 0. Consequently,even if magnetizations rotate upon application of the signal magneticfield, only a slight change results in the angle between themagnetizations of the two ferromagnetic films, and so the resistancechange is also subtle.

Furthermore, the ferromagnetic coupling acting between the twoferromagnetic films when the film thickness of the nonmagnetic film isdecreased causes deterioration in permeability. The NiFe film havinggood soft magnetic characteristics has a normal anisotropicmagnetoresistance effect. However, in a system in which a sense currentis flowed in a direction perpendicular to a signal magnetic field, whenthe signal magnetic field is 0 and the magnetizations of twoferromagnetic films point in the same direction, the anisotropicmagnetoresistance effect obtained by the signal magnetic field and theresistance change obtained by spin-dependent scattering cancel eachother out, as shown in FIG. 2.

Common problems of the artificial lattice film and the spin valvestructure will be described below. First, in order to obtain a highsensitivity in a magnetic head, a current to be supplied must beincreased as large as possible. If the current is increased in either ofthe film structures, however, the magnetization directions of someferromagnetic films are disturbed by a magnetic field produced by thiscurrent, preventing a highly sensitive resistance change with respect tothe magnetic field. More specifically, the magnetization readily pointsin the direction of the current magnetic field in the vicinities of theuppermost and lowermost layers of the stacked film, so the currentmagnetic field is strong in these portions.

Second, there are serious problems, such as the Barkhausen noisesuppression and operating point bias, to be solved in applying the filmto a magnetic head.

As described above, no existing magnetoresistance effect elements withthe artificial lattice film or the spin valve structure usingspin-dependent scattering can exhibit both good soft magneticcharacteristics and a high resistance change rate ΔR/R, which areessential to obtain a high sensitivity, even upon supply of a largecurrent.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation and has as its object to provide a magnetoresistance effectelement which has a film with a spin valve structure or an artificiallattice film having good soft magnetic characteristics, and which can beapplied to a high-sensitivity magnetic head.

In a magnetoresistance effect element which has a film with a spin valvestructure or an artificial lattice film having good soft magneticcharacteristics, and which can be applied to a high-sensitivity magnetichead, Co, CoFe, CoNi, NiFe, sendust, NiFeCo, Fe₈ N and the like may beused as a material of a ferromagnetic film. It is preferable that athickness of the ferromagnetic film falls in the range of 1 to 20 nm. Inthe magnetoresistance effect element, a nonmagnetic metal such as Mn,Fe, Ni, Cu, Al, Pd, Pt, Rh, Ru, Ir, Au or Ag and an alloy such as CuPd,CuFt, CuAu, CuNi, as a material of a nonmagnetic film. It is preferablethat a thickness of the nonmagnetic film falls in the range of 0.5 to 20nm, more preferably 0.8 to 5 nm.

According to the first aspect of the present invention, there isprovided a magnetoresistance effect element comprising a stacked filmformed on a substrate by sequentially stacking a ferromagnetic filmconsisting primarily of at least one elements selected from the groupconsisting of Co, Fe, and Ni, a nonmagnetic film, and aboveferromagnetic film, wherein the two ferromagnetic films are not coupledwith each other, and the closest packed plane of each ferromagnetic filmis oriented in a direction perpendicular to the film surface. Inparticular, it is desired that the ferromagnetic films made of Co_(1-x)Fe_(x) (0<×≦0.4) exhibit high ΔR/R and low Hc.

In the first aspect, "the two ferromagnetic films are not coupled witheach other" means that essentially no antiferromagnetic exchangecoupling exists between the two ferromagnetic films in other wordsantiparallel magnetization allinement must be stabilized by anothermethod (e.g. the use of a bias film). The term "closest packed plane"means (111) plane for fcc phase, and (001) plane for hcp phase.

In the first aspect of the invention, the method of orienting theclosest packed plane of the ferromagnetic film in the directingperpendicular to the film surface can be selected from: a method ofadding to the material of the ferromagnetic film at least one elementselected from the group consisting of Pd, Al, Cu, Ta, In, B, Nb, Hf, Mo,W, Re, Ru, Rh, Ga, Zr, It, Au, and Ag (of these elements, Pd, Cu, Au andAg are particular desirable since they cause virtually no decrease inresistance change rate), a method of using the C face of a sapphiresubstrate as the substrate on which the ferromagnetic film is formed,and a method of forming, between the substrate and the ferromagneticfilm, an undercoating film made of a material selected from the groupconsisting of material having fcc lattice, such as materials which fcc(face centered cubic) Bravais lattice or rhombohedral Bravais lattice(e.g., Cu, Ni, CuNi, NiFe, NiO, Ge, Si, GaAs), Ti, a magnetic amorphousmetal (e.g., CoZrNb, CoHfTa or the like), and a non-magnetic amorphousmaterial.

More specific examples of the material of the above undercoating filmare, when a ferromagnetic film having an fcc phase, such as a Co₉₀ Fe₁₀film, is used as the Co-based ferromagnetic film, a metal system havingthe fcc phase, such as a Cu-based alloy, such as Cu-Ge-Zr, Cu-P,Cu-P-Pd, Cu-Pd-Si, Cu-Si-Zr, Cu-Ti, Cu-Sn, Cu-Ti-Zr, and Cu-Zr; anAu-based alloy, such as Au-Dy, Au-Pb-Sb, Au-Pd-Si, and Au-Yb; anAl-based alloy, such as Al-Cr, Al-Dy, Al-Ga-Mg, and Al-Si; a Pt-basealloy, a Pd-based alloy, such as Pd-Si and Pd-Zr, a Be-based alloy, suchas Be-Ti, Be-Ti-Zr, and Be-Zr; a Ge-based alloy, such as Ge-Nb andGe-Pd-Se; an Ag-based alloy, an Rh-based alloy, an Mn-based alloy, anIr-based alloy, and a Pb-based alloy, an alloy system consistingprimarily of these metals having the fcc phase; a material having adiamond structure, such as Ge, Si, and diamond; and a material having azinc-blende structure, such as GaAs, Ga-Al-As, Ga-P, and In-P. It ispossible to use a material consisting primarily of at least onesubstance selected from these substances or a material formed by alsoadding other elements to any of these substances. Of the abovematerials, substances other than the single-element metal have an effectof suppressing the shunt current component because the substancesthemselves have specific resistances much higher than that of theferromagnetic film. The increase in the specific resistance by theaddition of other elements to the single-element metal can be obtainedby various combinations. Examples are a Cu-based alloy, such as Cu-Ni,Cu-Cr, and Cu-Zr, and other alloys, such as Au-Cr, Fe-Mn, Pt-Mn, andNi-Mn.

Examples of the nonmagnetic amorphous material are a nonmagnetic metalmaterial, such as a nonmagnetic single-element metal or alloy and amaterial containing a non-metal as an additive, amorphous Si, such ashydrogenated Si, and a nonmagnetic nonmetallic material, such asamorphous carbon, e.g., hydrogenated carbon, glassy carbon, and graphitecarbon.

The film thickness of the undercoating film is not particularly limited,but it is preferably 100 nm or less. This is so because even if thethickness of the undercoating film is increased to be larger than theabove value, no larger effect can be obtained, and, conversely, theproportion of a current flowing through the undercoating film increasesin the overall element, resulting in a decrease in resistance changerate. For nonmagnetic amorphous undercoating film, since it is possibleto grow this undercoating film in the form of a layer regardless of thetype of the material of the substrate, a smooth surface can be obtainedstably. In addition, the nonmagnetic amorphous undercoating film andhence has no adverse magnetic effect on the stacked film, i.e., the MRelement which is formed on the undercoating film and in which thenonmagnetic film is interposed between the ferromagnetic films.

When the undercoating film is formed, it may have improved crystalorientation but may have a reduced surface smoothness and, hence, adecrease in the resistance change rate. Hence, it is desirable that theundercoating film be made of two films, the first of which improvescrystal orientation in the closest packed plane, and the second of whichis made of Ti, Ta, Zr or nonmagnetic amorphous metal for enhancing theplane smoothness and which is interposed between the first undercoatingfilm and the substrate when the first undercoating layer is made of amaterial having fcc phase or magnetic amorphous metal. With thisarrangement, there can be provided a magnetoresistance effect elementhaving both good soft magnetic characteristics resulting from theimprovement in the crystal orientation in the closest packed plane andthe high rate of change in magnetic resistance. In addition, in thistwo-layered structure, the use of a second undercoating film having thesame crystal system as that of the ferromagnetic film and consisting ofa material having a higher specific resistance than that of theferromagnetic film makes it possible to decrease the shunt currentcomponent of the current flowing through the element as well asachieving the above effect. When the undercoating film has a stackedstructure of two or more layers, it is desirable that the film thicknessof this stacked film do not exceed 100 nm.

As the method of forming the undercoating film as described above, it ispossible to apply various film formation processes, such as aconventional sputtering process using RF discharge at 13.56 MHz, or 100MHz or higher, ion beam sputtering processes using various ion sources,e.g., an ECR ion source and a Kaufmann ion source, a vacuum depositionprocess using an electron beam evaporation source or a Knudesen cell, athermal CVD process, CVD processes using various plasmas, and an MOCVDprocess or an MOMBE process using an organometallic compound as amaterial. It is important in all of these film formation processes tocontrol water and oxygen by evacuation of up to an ultra-high vacuum andrealization of a very high purity of a material gas. More specifically,the contents of H₂ O and O₂ are reduced to preferably the order of ppmor less, and more preferably the ppb order.

In the first aspect of the invention, the material of the ferromagneticfilm contains as its main constituents at least one elements selectedfrom the group consisting of Co, Fe, and Ni. In particular, Co_(100-x)Fe_(x) (5≦×≦40) is preferred. This is so because it can readily achievelow Hc and high resistance change, while magnetic films without Co doesnot show much higher ΔR/R than NiFe films and magnetic films composed ofonly Co dose not show the remarkable improvement of the soft magneticproperties, such as low Hc, because of large crystal magneticanisocropy, regardless of the closest packed plane orientation.

As for the crystal orientation of the ferromagnetic film, a half-widthof a rocking curve of a reflection peak of a (111) plane, as the closestpacked plane, in an X-ray diffraction curve is preferably less than 20°,and most preferably 7° or less.

Representative examples of the substrate material are a single-crystalsubstance, such as MgO, sapphire, diamond, graphite, silicon, germanium,SiC, BN, SiN, AlN, BeO, GaAs, GaInP, GaAlAs, and BP, a polycrystallinesubstance of any of these single-crystal substances, a sintered bodycontaining any of these single-crystal substances as its mainconstituent; and a single-crystal substance, a polycrystallinesubstance, and a sintered body of a magnetic or nonmagnetic metal. Thesubstrate material is selected in accordance with the type of theferromagnetic film and the material of the undercoating film. Use of theC face of a sapphire substrate as the substrate is most preferablebecause it is well lattice-matched with Co-based magnetic film andlikely to have a smooth surface. When a single-crystal substrate, suchas a sapphire substrate, is used, the thickness of the ferromagneticfilm is preferably 20 nm or less. This is so because if the thickness ofthe ferromagnetic film exceeds 20 nm, the (111) orientation is degraded.

In the magnetic film which is (111)-oriented, Hc increases abruptly whenthe magnetization direction inclines slightly from the (111) plane.Therefore, even if the (111) orientation is realized, the magnetizationdirection sometimes falls outside the range of the (111) plane, so Hcdoes not decrease if undulations are present on the substrate surface.For this reason, the surface roughness of the substrate is preferablyless than 5 nm.

Note that the arrangement of the magnetoresistance effect element of thefirst aspect is not limited to the above arrangement but may be oneformed by alternately stacking nonmagnetic films and ferromagnetic filmsa plurality of number of times.

The second aspect of the present invention provides a magnetoresistanceeffect element comprising a stacked film formed on a substrate bysequentially stacking a ferromagnetic film consisting primarily of atleast one element selected from the group consisting of Co, Fe, and Ni,a nonmagnetic film, and above ferromagnetic film, wherein the materialof the ferromagnetic film contains at least one element selected fromthe group consisting of Pd, Al, Cu, Ta, In, B, Nb, Hf, Mo, W, Re, Ru,Rh, Ga, Zr, It, Au, and Ag. Of these elements which cause virtually nodecrease in resistance change rate are particularly desirable for threereasons. First, they do not form an intermetallic compound. Second, theferromagnetic film will be lattice-matched well with the intermediatenonmagnetic film (Cu or the like). Third, large spin-dependentscattering can be expected to occur due to so-called "bulk scattering."In the second aspect, a content of the additional element is set withinthe range in which a CoFe alloy exhibit a ferromagnetic property at roomtemperature. For example, it is preferable that a content of theadditional element is less than 6.5 at % in a case of Al, Ga, or In,that a content of the additional element is less than 10 at % in a caseof Nb, Ta, Zr, Hf, B, Mo, or W, and that a content of the additionalelement is less than 40 at % in a case of Cu, Pd, Au, Ag, Re, Ru, Rh, orIr.

The arrangement of the magnetoresistance effect element of the secondaspect of the invention is not limited to the above arrangement but maybe one formed by alternately stacking nonmagnetic films andferromagnetic films a plurality of number of times.

The third aspect of the present invention provides a magnetoresistanceeffect element comprising a stacked film formed on a substrate bysequentially stacking a ferromagnetlc film, a nonmagnetic film andanother ferromagnetic film, wherein each ferromagnetic film is comprisedof five or less layers, a ferromagnetic film having a resistivity of 50μΩ·cm or more is formed on upper layer of the stacked film and/orbetween the substrate and lower layer of the stacked film.

In the third aspect, the high-resistance magnetic film means aferromagnetic film or a magnetic film having ferromagnetism, Inaddition, the ferromagnetic film is limited to the stacked filmconstituted by five or less layers. This is because, if the interfacebetween the ferromagnetic film and the nonmagnetic film increases, theinterface between the high-resistance magnetic film and theferromagnetic film become less active, failing to the effect of theincrease in the ratio ΔR/R.

By stacking the films such that the high-resistance magnetic film is incontact with the ferromagnetic film, occurrence of magnons in theinterface can be prevented. If, however, the resistivity of the materialof this high-resistance magnetic film is less than 50 μΩ·cm, a currentflows mainly through the high-resistance magnetic film, undesirablydecreasing the resistance change rate. In other words, it is possible toprevent the current from being shunted to the high-resistance magneticfilm by using a ferromagnetic film or a magnetic film havingferromagnetism which has a resistivity of 50 μΩ·cm or more.

As a material of the high-resistance magnetic film, Ni, Fe, Co, NiFe,NiFeCo, CoFe, Co-based alloy, containing an additional element such asTi, V, Cr, Mn, Zn, Nb, Tc, Hf, Ta, W, Re, and the like may be used.

In the third aspect, the high-resistance magnetic film is preferably ahigh-resistance soft magnetic film. As the high-resistance soft magneticfilm, it is possible to use a high-resistance amorphous film consistingof, e.g., CoZrNb, a fine-crystal high-resistance soft magnetic filmconsisting of, e.g., FeZrN or CoZrN, or a film consisting of a materialin which X of NiFeX is one element selected from the group consisting ofRh, Nb, Zr, Hf, Ta, Re, It, Pd, Pt, Cu, Mo, Mn, W, Ti, Cr, Au, and Ag.Of these films, the amorphous film or the film consisting of thematerial consisting of CoZrN or NiFeNb and having an fcc phase isdesirable because the film promotes the fcc (111) orientation of theferromagnetic film formed on it.

The film thickness of the high-resistance magnetic film preferablyranges between 0.5 nm or more. This is because if the film thickness isless than 0.5 nm, the magnetism of the high-resistance magnetic filmitself is weakened to make prevention of occurrence of magnonsdifficult. In the case where the high-resistance magnetic film isinferior to the adjacent ferromagnetic film in terms of soft magneticcharacteristic, it desirably has a thickness of 10 nm or less. This isbecause a film thickness exceeding 10 nm has an influence on themagnetization process of the ferromagnetic film, and this makes itdifficult to obtain soft magnetic characteristics.

In the third aspect of the invention, usable examples of the material ofthe ferromagnetic film are Co, CoNi, CoFe, NiFe, and NiFeCo. The filmthickness of the ferromagnetic film preferably ranges from 1 to 20 nm.

In the third aspect, the high-resistance magnetic film can be formed asthe uppermost layer.

The arrangement of the magnetoresistance effect element according to thethird invention is not limited to the above arrangement but may be oneformed by alternately stacking nonmagnetic films and ferromagnetic filmsfive times or less. The magnetoresistance effect element of the thirdinvention is also suitable for the spin valve structure.

The fourth aspect of the present invention provides a magnetoresistanceeffect element comprising a stacked film formed on a substrate bysequentially stacking a ferromagnetic film, a first nonmagnetic film andanother ferromagnetic film, wherein each ferromagnetic film is comprisedof five or less layers, a second nonmagnetic film having a resistivitytwice or less that of the ferromagnetic film is formed on upper layer ofthe stacked film and/or between the substrate and lower layer of thestacked film, and the magnetic film in contact with the secondnonmagnetic film has a thickness of less than 5 nm.

In the fourth aspect, the material of the second nonmagnetic filmpreferably has the same crystal structure as that of the material of theferromagnetic film (e.g., when the ferromagnetic film consists of amaterial having the fcc phase, the first nonmagnetic film also consistsof a material having the fcc phase). In this case, it is preferable thatthe difference in lattice constant between the material of the secondnonmagnetic film and the material of the ferromagnetic film be 5% orless. This is so because the ferromagnetic film can be epitaxially grownby increasing the crystal matching properties between the ferromagneticfilm and the second nonmagnetic film, and this can suppress scatteringof electrons in the interface.

In the fourth aspect, as the material of the second nonmagnetic film, itis possible to use a material consisting primarily of at least oneelement selected from the group consisting of Mn, Fe, Ni, Cu, Al, Pd,Pt, Rh, It, Au, and Ag. It is also possible to interpose a secondundercoating film between the substrate and the second nonmagnetic film.Cu, Ag, Au, CuPd, CuPt, CuAu, or CuNi may be used as a material of thefirst nonmagnetic film. It is preferable that a thickness of the firstnonmagnetic film falls the range of 0.5 to 20 nm.

In the fourth invention, when two or more ferromagnetic films arepresent, it is desirable that the grain size of the crystal of thematerial constituting the ferromagnetic films be large in the directionof the film thickness so as not to interfere with crystal growth in eachferromagnetic film. If the ferromagnetic film is constituted by six ormore, the spin-dependent scattering interface increases, and theadvantage of the invention will not be attained in effect.

The film thickness of the second nonmagnetic film preferably rangesbetween 0.2 and 20 nm. If the film thickness of the second nonmagneticfilm is less than 0.2 nm, a probability that electrons flowing into thesecond nonmagnetic film undergo inelastic scattering in the interfacewith the substrate increases, and this makes it difficult to effectivelyextend the mean free path. If, on the other hand, the film thicknessexceeds 20 nm, no larger effect can be obtained, and a current flowingonly through the second nonmagnetic film increases to make it difficultto obtain a high change rate.

In the spin valve type magnetoresistance effect element according to thefourth aspect, the nonmagnetic film is so stacked as to contact at leastthe ferromagnetic film whose magnetization is not locked by theantiferromagnetic film. By stacking the nonmagnetic film in contact withthe ferromagnetic film, electrons flow into the nonmagnetic film even ifthe thickness of the ferromagnetic film is less than 5 nm, and this cankeep the effective mean free path of electrons long.

When the magnetoresistance effect element of the fourth aspect of theinvention is applied to a sensor, the material of the first nonmagneticfilm has a resistivity preferably twice or less, and more preferablylower that of a CoFe alloy as the material of the ferromagnetic film forthe reason explained below. That is, if the bulk resistivity of thefirst nonmagnetic film is significantly higher than that of theferromagnetic film, electrons flowing into the nonmagnetic film undergoscattering, and consequently the effective mean free path can no longerbe kept long.

The resistivity of the material of the first nonmagnetic film ispreferably 1/4 or more the resistivity of the ferromagnetic film, sinceif the resistivity of the material of the second nonmagnetic film isless than 1/4 the resistivity of the ferromagnetic film, a currenteasily flows into the second nonmagnetic film.

In the fourth aspect, the first nonmagnetic film may be formed as theuppermost layer.

The arrangement of the magnetoresistance effect element of the fourthaspect is not limited to the above arrangement but may be one formed byalternately stacking second nonmagnetic films and ferromagnetic films aplurality of number of times. In addition, the magnetoresistance effectelement of the fourth invention can have either the spin valve structureor the artificial lattice film structure.

The fifth aspect of the present invention provides a magnetoresistanceeffect element comprising a stacked film formed on a substrate bysequentially stacking a ferromagnetic film, a nonmagnetic film, andanother ferromagnetic film, and a thin film formed on upper layer of thestacked film and/or between the substrate and lower layer of the stackedfilm, and having a resistivity higher than that of the ferromagneticfilm and a mean free path longer than that of the ferromagnetic film.

In the fifth aspect, examples of the material of the thin film are asemimetal, such as Bi, Sb, and carbon, a semiconductor degenerated bydoping at a high concentration, and an oxide semiconductor, such as SnO₂and TiO₂. The film thickness of the thin film is preferably 1 to 50 nmfor the reason explained below. That is, if the film thickness of thethin film is less than 1 nm, the effect of increasing the mean free pathof electrons cannot be obtained satisfactorily. If the film thicknessexceeds 50 nm, on the other hand, no larger effect can be obtained, anda current flowing through the thin film increases to make it difficultto obtain a high change rate.

In the fifth invention, the mean free path means the average of thedistances electrons travel without scattered by any other thing.

In the fifth aspect, if the resistivity of the thin film is lower thanthat of the ferromagnetic film, a current flows into the thin film,weakening the magnetoresistance effect. Therefore, the thin film isformed to have a resistivity higher than that of the ferromagnetic film.

In the fifth aspect, in order to increase the resistivity of the entirestacked film, the film thickness of ferromagnetic film in contact withthe thin film is set at preferably 5 nm or less, whereas the filmthickness of the ferromagnetic film not in contact with the thin film isset to fall within the range of 2 to 20 nm in order to keep a requiredmean free path.

The arrangement of the magnetoresistance effect element of the fifthaspect is not limited to the above arrangement but may be one formed byalternately stacking nonmagnetic films and ferromagnetic films aplurality of number of times.

The sixth aspect of the present invention provides a magnetoresistanceeffect element comprising an undercoating film formed on a substrate andhaving the fcc phase, and a stacked film obtained by sequentiallystacking a ferromagnetic film formed on the undercoating film andconsisting of a CoFe alloy, a nonmagnetic film, and anotherferromagnetic film, wherein the undercoating film consists of a materialwith a larger lattice constant than that of the material of theferromagnetic film.

Note that no decrease in Hc was found when a Co film was formed on aglass substrate via a Cu undercoating film. This indicates that theeffect of improving soft magnetism using an undercoating film isachieved when a ferromagnetic film consists of an alloy obtained byadding Fe to Co. It was found that a low Hc was realized especially whenthe concentration of Fe to be added to Co was 5% to 40%. This is sobecause if the Fe concentration is less than 5%. the hcp phase is mixed,and, if the Fe concentration exceeds 40%, the bcc phase is mixed easilyand the lattice mismathcing occurs. Examples of elements to be added toCoFe are Ni, Pd, Al, Cu, Ta, In, B, Zr, Nb, Hff, Mo, W, Re, Ru, Ir, Rh,Ga, Au, and Ag. The Hc reducing effect can be achieved similarly whenthese elements were added.

In the sixth aspect of the invention, the undercoating film preferablyconsists of a material with a higher resistivity than that of the CoFealloy constituting the ferromagnetic film. It is also preferable that afilm for improving smoothness be formed between the substrate and theundercoating film. As the film for improving smoothness, a filmconsisting of, e.g., Cr, Ta, Zr, Ti or the like can be used.

It is also preferable that the undercoating film thickness is less than20 nm because the sense current in the undercoating film can keep small.

Note that the arrangement of the magnetoresistance effect elementaccording to the sixth invention is not limited to the above arrangementbut may be one formed by alternately stacking nonmagnetic films andferromagnetic films a plurality of number of times.

The seventh aspect of the present invention provides a magnetoresistanceeffect element comprising a unit stacked film formed on a substrate andconstituted by (a first ferromagnetic film/a first nonmagnetic film)_(n)(n≧1)/a first ferromagnetic film, and a second ferromagnetic film formedon the unit stacked film via a second nonmagnetic film having athickness different from that of the first nonmagnetic film, wherein themagnetizations of the individual ferromagnetic films of the unit stackedfilm are ferromagnetically coupled with each other. The secondferromagnetic film may be above unit stacked film or may be singlelayered ferromagnetic film.

In the seventh aspect, the first nonmagnetic film of the unit stackedfilm preferably has a thickness of 2 nm or less, by which no RKKY-likeantiferromagnetic coupling is caused, since the magnetizations of theindividual ferromagnetic films in the unit stacked film can be kept in aferromagnetically coupled state. As an example, if the material of theferromagnetic film is CoFe and the material of the first nonmagneticfilm is Cu, the thickness of the first nonmagnetic film is set at avalue not in the vicinity of 1 nm. It is preferable that a thickness ofthe second nonmagnetic film falls the range of 0.5 to 20 nm.

In addition, it is desirable that the ferromagnetic film and the firstnonmagnetic film the grown while maintaining the lattice matching, i.e.,the ferromagnetic film and the nonmagnetic film be lattice-matched tocause no excess scattering in the interface between them. This canprevent an increase in the resistance.

Note that the arrangement of the magnetoresistance effect element of theseventh aspect is not limited to the above arrangement but may be oneformed by alternately stacking nonmagnetic films and ferromagnetic filmsa plurality of number of times. Note also that the magnetoresistanceeffect element of the seventh aspect is applicable to both the spinvalve structure and the artificial lattice film structure.

The eighth aspect of the present invention provides a magnetoresistanceeffect element comprising a stacked film formed on a substrate bysequentially stacking a ferromagnetic film, a nonmagnetic film, andanother ferromagnetic film, wherein each of magnetization of twoadjacent ferromagnetic films is rotated in the reverse direction eachother when a bias magnetic field in the reverse direction is applied toeach of two ferromagnetic films by using a bias magnetic film as atleast one bias magnetic field.

In the eighth aspect of the invention, the method of applying the biasmagnetic fields to cause the each magnetization direction of the twoferromagnetic films to rotate in the reverse direction can be used amethod using exchange coupling from an antiferromagnetic film and alsousing a hard magnetic film, or a method using an exchange bias producedby stacking a ferromagnetic film onto the ferromagnetic film in thestacked film as a biasing means to be applied to one ferromagnetic filmsand can be used a method using a bias magnetic field generated by acurrent, static coupling (a demagnetizing field) generated when a finepattern is processed as a biasing means to be applied to anotherferromagnetic film.

More specifically, antiferromagnetic films are stacked on the individualferromagnetic films, and the ferromagnetic films are magnetized by usingthe antiferromagnetic films in a way which produces a difference of 180°in the direction of the bias magnetic field between the two adjacentferromagnetic films. This magnetization can be achieved by, e.g., amethod in which the direction of the application of the static magneticfield in the formation of the antiferromagnetic films is changed by 180°from that in the formation of the ferromagnetic films. In this case, itis desirable that the magnitude of the bias magnetic field to be appliedto the neighboring ferromagnetic films be a minimum value required toform a single domain in the ferromagnetic film, e.g., 5 kA/m or less. Inaddition, the two antiferromagnetic films preferably have different Neel temperature in order to easily apply a bias magnetic field indifferent direction each other to each of ferromagnetic film.

The following method is also usable as an alternative. That is, anexchange bias magnetic field generated by stacking the antiferromagneticfilm is used in application of the bias magnetic field to oneferromagnetic film. In application of the bias magnetic field to theother ferromagnetic film, another ferromagnetic film is stacked on theremaining film surface of the antiferromagnetic film, and a staticcoupled magnetic field (a demagnetizing field) generated when thisferromagnetic film whose magnetization is locked by theantiferromagnetic film is formed into a fine pattern is used. This newferromagnetic film preferably has a two-layered structure formed bystacking a ferromagnetic film A (e.g., a film consisting of a materialwith a high crystallinity, such as NiFe or CoFe) suitable forapplication of the exchange bias, on the side in contact with theantiferromagnetic film, and a ferromagnetic film B (e.g., a Co-basedamorphous ferromagnetic film or a nitride or carbide fine-crystalferromagnetic film) suitable for generating the static coupled magneticfield onto the ferromagnetic film A, so as to cause ferromagneticexchange coupling between them. With this two-layered structure, it ispossible to adjust the Bs or the resistance (e.g., to increase the Bsand increase the resistance) of the ferromagnetic film B by controllingthe film thickness, the composition, and the formation conditions of theferromagnetic film B, thereby adjusting the strength of the staticcoupled bias magnetic field or a shunt bias (operating point bias)generated when a portion of a sense current flows through theferromagnetic film B. When using NiFe films with the anisotropicmagnetoresistance as a ferromagnetic film it is preferable that a sensecurrent is made to flow in a direction perpendicular to a direction of asignal current.

In applying a bias magnetic field to a ferromagnetic film by using anantiferromagnetic film, a problem arises if the bias magnetic field istoo large. However, this large bias magnetic field can be decreased byinterposing, between the antiferromagnetic film and the ferromagneticfilm, a stacked film of a ferromagnetic film and a nonmagnetic film inwhich the ferromagnetic film is present on the antiferromagnetic filmside.

In the conventional spin valve film, if the nonmagnetic film is 2 nm orless thick, the ferromagnetic coupling between the ferromagnetic filmsspaced apart by the nonmagnetic film is strengthened, making it nolonger possible to antiparallel magnetization alignment. Nonetheless, inthe eighth aspect of the present invention, the bias magnetic field canbe strengthened more than the ferromagnetic coupling field describedabove even if the nonmagnetic film has a thickness of 2 nm or less. As aresult, the antiparallel magnetization alignment can be achieved. Thespin valve can obtain a higher ΔR/R than the conventional spin valve.

The magnetoresistance effect element of the eighth to eleventh aspectsof the invention is not limited to the embodiment described above.Rather, the element may be one which is formed by alternately stackingnonmagnetic films and ferromagnetic films, a number of times.

The ninth aspect of the present invention provides a magnetoresistanceeffect element comprising a stacked film on a substrate by sequentiallystacking a magnetization-locked film which magnetization substantiallycan not rotate by a signal magnetic field, nonmagnetic film and afield-detecting film which detects a signal by the change in amagnetization based on the signal magnetic field, wherein, when saidsignal magnetic field has no intensity, each of the magnetizationdirection of said magnetization-locked film and said field-detectingfilm is substantially perpendicular to each other, and a sense currentis made to flow in a direction which is substantially identical to thedirection of the signal magnetic field.

In the ninth aspect of the invention, the magnetization of theantiferromagnetic film may be locked in various methods. Among thesemethods are: method of forming the film on the magnetization-locked filmin exchange-coupled connection; method of increasing the Hc value; andmethod of forming a high-Hc ferromagnetic on the magnetization-lockedfilm. One of two alternative methods may be used to make themagnetization directions of two magnetic films intersect with eachother. The first method is to impart an easy axis of magnetization tothe magnetic-field detecting magnetic film, which intersects with themagnetization direction of the magnetization-locked film. The secondmethod is to apply a small exchange-coupled bias (e.g., 5 kA/m or less)in the direction at right angles to the magnetization direction of themagnetization-locked film. In the second method, it is preferable, forCoFe films with larger anisotropy filed, that the easy axis of themagnetic field detecting film exists in the almost same direction of themagnetization of the magnetization-locked film and the bias field to themagnetic field detecting film is slightly larger than the anisotropyfield of the magnetic field detecting film. The second method is usefulto enhance the magnetic permeability of CoFe with larger anisotropyfield.

The tenth aspect of the present invention provides a magnetoresistanceeffect element comprising a bias film formed on a substrate, a firstferromagnetic film formed on the bias film to serve as amagnetization-locked film, a nonmagnetic film formed on the firstferromagnetic film, and a second ferromagnetic film formed on thenonmagnetic film to serve as a field detecting film, wherein themagnetization of the first ferromagnetic film is locked, and an angle θdefined between the magnetization direction of the first ferromagneticfilm and the magnetization direction of the second ferromagnetic film atnearly 0 signal field is 30° to 60°. The first ferromagnetic film mayserve as a field detecting film, and the second ferromagnetic film mayserve as a magnetization-locked film by replacing the bias film on thesecond ferromagnetic film.

As the magnetization locking means in the tenth invention, there is amethod in which an exchange bias produced by stacking anantiferromagnetic film onto a ferromagnetic film for lockingmagnetization or a ferromagnetic film is used as a high-coercive-forcefilm. The means for inclining the magnetization direction of the otherferromagnetic film for signal magnetic field detection from themagnetization locking direction can be selected from a method using theaxis of easy magnetization, application of a bias magnetic field from ahard magnetic film adjacent to the ferromagnetic film for signalmagnetic field detection, a static magnetic bias generated by aferromagnetic film stacked on the antiferromagnetic film formagnetization locking, and a current magnetic field from a sensecurrent. The angle of inclination is preferably 30° to 60°. To use themagnetic field from the field sense current, it is required to flow thesense current in substantially the same direction as the signal magneticfield. Note that in order to stabilize the magnetization lockingdirection, the sense current is desirably flowed such that the magneticfield from the sense current is applied in substantially the samedirection as the magnetization locking ferromagnetic film.

The eleventh aspect of the present invention provides amagnetoresistance effect element comprising a stacked film formed on asubstrate and constituted by (ferromagnetic film/nonmagnetic film), andat least two bias films layered on the uppermost ferromagnetic film inthe stacked film and/or under the lowermost ferromagnetic film in thestacked film, wherein a bias magnetic field for the purpose ofmagnetization-locking is applied to at least one ferromagnetic film, aminimum bias magnetic field required for the purpose of disappearance ofa magnetic domain is applied to at least one ferromagnetic film.

In the eleventh aspect, a bias magnetic field generated by some othermeans may be applied to the particular ferromagnetic film in a directionalmost perpendicular to the above bias magnetic field. The ferromagneticfilm applied with the bias magnetic field generated by that other meansneed not have an easy axis of magnetization.

In the eleventh aspect, the bias films may be formed on uppermostferromagnetic film of the stacked film and between the substrate and thelowermost ferromagnetic film of the stacked film, respectively.Alternatively, the bias films may be formed on uppermost ferromagneticfilm or between the substrate and the lowermost ferromagnetic film.

In the eleventh aspect of the invention, it is preferable that thedirection of the bias magnetic field and the axis of each magnetizationof the ferromagnetic film applied with the bias magnetic field intersectat substantially right angles. Hence, it is possible to enhance themagnetic permeability (μ) of the Co-based alloy film having high Hk.

As the bias magnetic field in this eleventh invention, it is possible touse at least one type of a bias magnetic field selected from the groupconsisting of an exchange coupled magnetic field from anantiferromagnetic film, an exchange coupled magnetic field or a staticcoupled magnetic field from a ferromagnetic film, and a current magneticfield.

As a method of generating the exchange coupled magnetic field, a methodin which a ferromagnetic film is used as the bias film, and a film whichis made to reduce an exchange bias is formed between a ferromagneticfilm of the stacked film and the bias film, or a method in which aferromagnetic film is used as the bias film, and the bias film isdirectly formed on a ferromagnetic film of the stacked film, may beused. In the former case, it is preferable that a uniaxial magneticanisotropy (Hk) of the bias film is larger than that of theferromagnetic film of the stacked film, and that a coercive force (Hc)of the bias film is larger than that of the ferromagnetic film of thestacked film.

In the eleventh aspect, a bias magnetic field by which the magnetizationis essentially not moved by a signal magnetic field is applied to one ofthe uppermost and lowermost ferromagnetic films, and a magnetic field bywhich a signal magnetic field can be detected and Barkhausen noise canbe removed is applied to the other. Stacking of the antiferromagneticfilm is suitable for application of the former bias magnetic field.Stacking of the second ferromagnetic film or the antiferromagnetic filmis suitable for application of the latter bias magnetic field. Examplesof the second ferromagnetic film are a high-resistance soft magneticfilm which is given a single domain by some method and in which themagnetization directions are aligned in one direction (e.g., a Co-basedamorphous film heat-treated in a rotating magnetic field), a film with ahigh uniaxial magnetic anisotropy (e.g., a Co(Fe)-based amorphous filmheat-treated in a static magnetic field), and a high-coercive-forcefilm. A high-resistance soft magnetic film with a single domain can berealized by widening the second ferromagnetic film to be larger than theother films and stacking a hard magnetic film or an antiferromagneticfilm onto the edge portion of the widened film.

The twelfth aspect of the present invention provides a magnetoresistanceeffect element comprising a stacked film formed on a substrate byalternately stacking at least three ferromagnetic films and at least twononmagnetic films, wherein the magnetic permeabilities of the uppermostand lowermost ferromagnetic films serving as magnetization-locked filmsare lower than those of the other ferromagnetic films serving as fielddetecting films.

In the twelfth aspect, the method of decreasing the magneticpermeabilities of the uppermost and lowermost ferromagnetic films, i.e.,the method of locking the magnetizations can be selected from a methodusing an antiferromagnetic film, a method using a hard magnetic film,and a method using a demagnetizing field, like in the eighth invention.

The thirteenth aspect of the present invention provides amagnetoresistance effect element comprising a magnetoresistance effectelement including a high-coercive-force film in which a hexagonal C axisis present in the film surface, and a ferromagnetic film having acoercive force lower than that of the high-coercive-force film.

In the thirteenth aspect, the high-coercive-force film can also be usedas a film for applying a bias magnetic field. In addition,high-coercive-force films and intermediate films can be stacked aplurality of number of times.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a perspective view showing a conventional magnetoresistanceeffect element;

FIG. 2 is a graph showing the R-H curves of the conventionalmagnetoresistance effect element;

FIGS. 3, 10, and 17 are sectional views each showing a magnetoresistanceeffect element (with a spin valve structure) according to the firstinvention of the present invention;

FIG. 4 is a graph showing the external magnetic field dependency of theresistance change rate of the magnetoresistance effect element shown inFIG. 3;

FIGS. 5A and 5B are graphs showing the magnetization curves of themagnetoresistance effect element shown in FIG. 3;

FIG. 6 is a sectional view showing an embodiment of a magnetoresistanceeffect element (with an artificial lattice film) according to the firstinvention of the present invention;

FIG. 7 is a graph showing the external magnetic field dependency of theresistance change rate of the magnetoresistance effect element shown inFIG. 6;

FIG. 8 is a graph showing the film thickness dependency of the coerciveforce when a Co₉₀ Fe₁₀ film has a Cu undercoating film;

FIG. 9 is a graph showing the film thickness dependency of the coerciveforce when a Co₉₀ Fe₁₀ film does not have a Cu undercoating film;

FIG. 11A is a graph showing a θ-2θ scan X-ray diffraction curve on the Cface of a sapphire substrate, and FIG. 11B is a graph showing a θ-2θscan X-ray diffraction curve on the R plane of a sapphire substrate;

FIG. 12 is a graph showing a rocking curve related to the closest packedplane peak in Co₉₀ Fe₁₀ film/Cu film/sapphire substrate C face;

FIG. 13 is a graph showing the rocking curve half-width dependency ofthe coercive force of a Co₉₀ Fe₁₀ film upon closest packed planereflection;

FIG. 14 is a graph showing the Al concentration dependency of thecoercive force of (Co₉₀ Fe₁₀)_(1-x) Al_(x) film/Cu film;

FIG. 15 is a graph showing the closest packed plane reflection intensitydependency of the coercive force of Co₉₀ Fe₁₀ film/Cu film;

FIG. 16 is a graph showing the Ta concentration dependency of thecoercive force of (Co₉₀ Fe₁₀)_(1-x) Ta_(x) film/Cu film;

FIGS. 18 and 24 are sectional views each showing a magnetoresistanceeffect element according to the third invention of the presentinvention;

FIG. 19 is a graph showing the M-H curves in the axis of easymagnetization of the magnetoresistance effect element shown in FIG. 18;

FIG. 20 is a graph showing the M-H curves in the axis of hardmagnetization of the magnetoresistance effect element shown in FIG. 18;

FIG. 21 is a graph showing the R-H curves of the magnetoresistanceeffect element shown in FIG. 18;

FIG. 22 is a graph showing the M-H curves in the axis of easymagnetization of a magnetoresistance effect element having nohigh-resistance amorphous layer;

FIG. 23 is a graph showing the M-H curves in the axis of hardmagnetization of the magnetoresistance effect element having nohigh-resistance amorphous layer;

FIGS. 25A to 25C are sectional views showing a manufacturing process ofanother example of the magnetoresistance effect element according to thethird invention of the present invention;

FIG. 26 is a perspective view showing still another example of themagnetoresistance effect element according to the third invention of thepresent invention;

FIG. 27 is sectional views each showing an example of amagnetoresistance effect element according to the fourth invention ofthe present invention;

FIG. 28 is a graph showing the relationship between the Δρ/ρ0 and thed_(CoFe) of the magnetoresistance effect element shown in FIG. 27;

FIG. 29 is a sectional view showing a magnetoresistance effect elementaccording to the fifth invention of the present invention;

FIG. 30 is a sectional view showing another magnetoresistance effectelement according to the fifth invention of the present invention;

FIGS. 31, 32, and 45 are graphs each showing the dependency of thecoercive force upon the film thickness of a ferromagnetic film in amagnetoresistance effect element according to the sixth invention of thepresent invention;

FIGS. 33 and 36 are graphs each showing the magnetization curves of theferromagnetic film of the magnetoresistance effect element according tothe sixth invention of the present invention;

FIG. 35 is a graph showing the relationship between the saturationmagnetic field Hx and the Cu film thickness in the ferromagnetic film ofthe magnetoresistance effect element according to the sixth invention ofthe present invention;

FIGS. 37 and 45 are sectional views each showing a magnetoresistanceeffect element according to the fourth invention of the presentinvention;

FIG. 39 is a graph showing the magnetization curves of themagnetoresistance effect element shown in FIG. 37;

FIG. 40 is a graph showing the resistance change characteristics of themagnetoresistance effect element shown in FIG. 37;

FIG. 41 is a graph showing the magnetization curves of a conventionalmagnetoresistance effect element;

FIG. 42 is a graph showing the resistance change characteristics of theconventional magnetoresistance effect element;

FIGS. 43A and 43B are graphs showing the magnetization curves of aferromagnetic film having a Cu undercoating film in a magnetoresistanceeffect element according to the seventh invention of the presentinvention;

FIG. 44 is a graph showing the resistance change characteristics of theferromagnetic film having the Cu undercoating film in themagnetoresistance effect element according to the seventh invention ofthe present invention;

FIG. 46 is a graph showing the magnetization curves of themagnetoresistance effect element shown in FIG. 45;

FIG. 47 is a graph showing the resistance change characteristics of themagnetoresistance effect element shown in FIG. 45;

FIG. 48 is a schematic view for explaining fluctuations in a film;

FIG. 49A is a graph showing the small angle reflection X-ray diffractioncurve of a Co₉₀ Fe₁₀ /Cu artificial lattice film on an MgO (110)-planesubstrate, and FIG. 49B is a graph showing the medium angle reflectionX-ray diffraction curve of the Co₉₀ Fe₁₀ /Cu artificial lattice film onthe MgO (110)-plane substrate;

FIG. 50A is a graph showing a rocking curve measured in the direction ofthe [110] axis for fcc (220) reflection shown in FIGS. 49A and 49B, and

FIG. 50B is a graph showing a rocking curve measured in the direction ofthe [100] axis for fcc (220) reflection shown in FIGS. 49A and 49B;

FIG. 51A is a perspective view showing the in-place distribution of anormal to a crystal orientation plane caused by fluctuations of thecrystal orientation plane, and FIG. 51B is a schematic view showing thesense current direction dependency of the resistance change rate;

FIG. 52A is a graph showing the magnetization curves of a 5.5 nm Cu/(1.1nm Cu/1 nm CoFe)₁₆ artificial lattice film in the direction of the [100]axis of an external magnetic field, and FIG. 52B is a graph showing themagnetization curves of the 5.5 nm Cu/(1.1 nm Cu/1 nm CoFe)₁₆ artificiallattice film in the direction of the [110] axis of the external magneticfield;

FIG. 53 is a graph showing the bias voltage dependency of the resistancechange rate of a Co₉₀ Fe₁₀ /Cu stacked film on an MgO (110)-planesubstrate;

FIG. 54 is a perspective view showing a state in which a stacking defectis introduced to a Co₉₀ Fe₁₀ /Cu stacked film oriented in the fcc-phase(111) plane;

FIG. 55 is a schematic view showing the arrangement of atoms when astacking defect is introduced to a Co₉₀ Fe₁₀ /Cu stacked film orientedin the fcc-phase (111) plane;

FIG. 56 is a schematic view showing the arrangement of atoms when atwinned crystal defect is introduced to a Co₉₀ Fe₁₀ /Cu stacked filmoriented in the fcc-phase (111) plane;

FIG. 57 is a schematic view showing the sense current directiondependency of the resistance change rate in the state shown in FIG. 56;

FIG. 58 is a graph showing the substrate bias dependency of theresistance change rate of a Co₉₀ Fe₁₀ /Cu artificial lattice film on aglass substrate;

FIG. 59 is a graph showing the bias dependency of the long periodicstructure reflection intensity of a Co₉₀ Fe₁₀ /Cu artificial latticefilm on a glass substrate;

FIG. 60 is a graph showing the bias dependency of the fcc-phase(111)-plane reflection intensity of a Co₉₀ Fe₁₀ /Cu artificial latticefilm on a glass substrate;

FIG. 61 is a graph showing the bias dependency of the coercive force ofa Co₉₀ Fe₁₀ /Cu artificial lattice film on a glass substrate;

FIGS. 62 to 67 are perspective views each showing a magnetoresistanceeffect element according to the eighth invention of the presentinvention;

FIG. 68 is a graph showing the resistance change characteristics of themagnetoresistance effect element according to the eighth invention ofthe present invention;

FIGS. 69 and 70 are perspective views each showing a magnetoresistanceeffect element according to the 12th invention of the present invention;

FIG. 71, FIGS. 72A to 72C, and FIG. 73 are perspective views eachshowing a magnetoresistance effect element according to the tenthinvention of the present invention;

FIG. 74 is a graph showing the resistance change characteristics of astacked film of the magnetoresistance effect element according to thetenth invention of the present invention;

FIG. 75 is a perspective view showing the magnetoresistance effectelement according to the 12th invention of the present invention;

FIG. 76 is a sectional view showing the magnetoresistance effect elementaccording to the 12th invention of the present invention;

FIGS. 77, 83, and 84 are sectional views each showing amagnetoresistance effect element according to the 13th invention of thepresent invention;

FIG. 78 is a graph showing the X-ray diffraction pattern of a Co/Crstacked film;

FIG. 79 is a graph showing the R-H curve of a stacked film formed at asubstrate temperature of about 100° C. according to the 13th inventionof the present invention;

FIG. 80 is a graph showing the R-H curve of a stacked film formed at asubstrate temperature of about 200° C. according to the 13th inventionof the present invention;

FIG. 81 is a graph showing the R-H curve of a stacked film according tothe 13th invention of the present invention when the pattern widthdirection is aligned with the axis of easy magnetization; and

FIG. 82 is a graph showing the R-H curves of a stacked film according tothe 13th invention of the present invention when an undercoating film isnot formed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the first invention of the present invention, good soft magneticcharacteristics can be obtained by orienting the closest packed plane,e.g., the fcc-phase (111) plane of a ferromagnetic film containing asits main constituents at least two types of elements selected from thegroup consisting of Co, Fe, and Ni in a direction perpendicular to thefilm surface. This is so because no magnetic anisotropy depending oncrystal magnetic anisotropy constant K₁ appears in the (111) plane. Inaddition, the magnetization of the ferromagnetic film can be kept in the(111) plane by controlling the surface roughness of a substrate fordepositing the ferromagnetic film, and this consequently decreases thecoercive force associated with the crystal magnetic anisotropy.Therefore, a good soft magnetism can be obtained. Furthermore, byperforming orientation such that the rocking curve half-width becomesless than 20°, preferably 7° or less, there can be provided ahigh-sensitivity magnetoresistance effect element having good softmagnetic characteristics with a coercive force (Hc) of at most 100 A/m,a high resistance change rate (ΔR/R) exceeding that of a non-orientedfilm or an oriented film (e.g., at 100)-oriented one), for example theΔR/R of a CoFe film of about 10%, and a high permeability.

On the other hand, it is possible to obtain a high-sensitivitymagnetoresistance effect element having soft magnetic characteristicswith Hc of at most 100 A/m and ΔR/R of 5% or more by adding additiveelements to a CoFe alloy. In particular, the soft magneticcharacteristics is improved markedly in the case of Al, Ta, Zr or Hr.Although the reason why the soft magnetic characteristics are improvedis still unclear, it is assumed that the effect obtained by reduction incrystal magnetic anisotropy contributes as well as the improvement incrystal orientation. In the case of Pd, Cu, Au or Ag added in themaximum possible amount of 40 at %, the metal does not form anintermetallic compound, the ferromagnetic film will be lattice-matchedwell with the intermediate nonmagnetic film (Cu or the like), andspin-dependent scattering can be expected to occur due to so-called"bulk scattering." Hence, the rate ΔR/R can be maintained at a highvalue.

In the first aspect of the invention, a smooth surface can be obtainedfor an amorphous nonmagnetic film formed as an undercoating film of theferromagnetic film regardless of the type of the material of asubstrate. This makes it possible to improve the surface smoothness ofthe ferromagnetic film formed on the amorphous nonmagnetic film and toimprove the smoothness of the interface with the nonmagnetic film.Therefore, a high resistance change rate can be obtained stably. Inaddition, since the undercoating film according to the present inventionis a nonmagnetic film, the film has no adverse effect on theferromagnetic film formed on it. Furthermore, the low coercive force andhigh ΔR/R can be achieved by forming on the smooth undercoating film andanother undercoating film with the effect of the crystal orientationimprovement between the ferromagnetic film and the substrate.

In the third aspect of the present invention, a ferromagnetic film whichproduces a resistance change and a high-resistance soft magnetic filmare formed with the exchange coupling. Therefore, as the magnetizationof the high-resistance soft magnetic film consisting of, e.g., anamorphous material with good soft magnetic characteristics rotates, themagnetization of the ferromagnetic film also rotates. This improves thesoft magnetic characteristics of the ferromagnetic film.

In addition, the use of the high-resistance soft magnetic filmsuppresses the reduction in the rate of change in magnetic resistancecaused by a shunt effect.

In the third aspect, generation of magnons in the interface is preventedby stacking a ferromagnetic film, or a ferromagnetic film in contactwith the ferromagnetic film. As a result, it becomes possible todecrease the probability of reversal of electron spins upon collision ofmagnons against electrons, and this increases the resistance change rateat room temperature. If, however, the specific resistance of the abovethin film is low, a large current flows into the stacked thin film,weakening the magnetoresistance effect. In the third invention,therefore, a ferromagnetic film, which has a specific resistance of 50μΩ·cm or more, is used as the material of the thin film, therebypreventing the shunt current. Consequently, a magnetoresistance effectelement with a high resistance change rate and a high sensitivity can berealized.

In the fourth aspect of the present invention, a nonmagnetic film isstacked in contact with at least one of ferromagnetic films, Therefore,even if the thickness of this ferromagnetic film is less than 5 nm, theeffective mean free path of electrons can be kept long. For example, ifthe thickness of a ferromagnetic film is decreased in a spin valve typestacked film, the resistivity increases and the resistance change ratedecreases. If, however, the thickness of a ferromagnetic film isdecreased and at the same time a nonmagnetic film is stacked in contactwith this thin ferromagnetic film, electrons can flow into thenonmagnetic film without undergoing inelastic scattering on the surfaceof the ferromagnetic film. That is, the thickness of the ferromagneticfilm can be decreased while maintaining the long effective mean freepath. To obtain the above effect of the present invention, the number ofmagnetic films must be five or more.

If, however, the thickness of the ferromagnetic film is decreased to beless than 5 nm in the case that the resistivity of the nonmagnetic filmis much higher than that of the ferromagnetic film, electrons flow intothe nonmagnetic film but immediately undergo scattering inside the film.This shortens the effective mean free path, leading to a decrease in theresistance change rate. That is, by stacking a nonmagnetic film with theresistivity equal to or lower than that of the ferromagnetic film incontact with the ferromagnetic film, a magnetoresistance effect elementwith a high resistance change rate can be obtained while the thicknessof the ferromagnetic film is decreased to be less than 5 nm. Therefore,even if a magnetic film is processed into a fine pattern incorrespondence with high-density magnetic recording and reproductionusing a narrow track width, this small thickness of the ferromagneticfilm can suppress occurrence of domain walls caused by a demagnetizingfield, thereby preventing Barkhausen noise. As a result, there can beprovided a noise-free, high-sensitivity magnetoresistance effect elementsuitable for reproduction of high-density recording.

In the fifth aspect of the present invention, by stacking a thin filmwith a long mean free path in contact with at least one of ferromagneticfilms, the effective mean free path of the whole stacked film can beprolonged. For example, the following is known as the physical mechanismof a magnetoresistance effect in a spin valve type stacked film. Thatis, in the spin valve type stacked film, if the magnetization directionsof two ferromagnetic films are parallel to each other, conductionelectrons having either a spin parallel to the magnetization or a spinantiparallel to the magnetization can have a long mean free path in thefilm as a whole, and the film exhibits a low resistivity as a whole. Incontrast, if the magnetizations of two ferromagnetic films areantiparallel to each other, no conduction electrons having a long meanfree path in the film as a whole can exits any longer, and theresistivity rises. The magnetoresistance effect of the spin valve typestacked film is determined by the difference in length of the mean freepath between these two states.

It is known that inside a ferromagnetic film, the mean free path ofelectrons having a spin parallel to the magnetization is different fromthat of electrons having a spin antiparallel to the magnetization. Forthe reason described above, as the mean free path that electrons in thespin direction, along which a longer mean free path is obtained inside aferromagnetic film, has is increased, the magnetoresistance effect ofthe spin valve type stacked film can be enhanced. In the fifthinvention, therefore, by stacking the thin film with a mean free pathlonger than that of the ferromagnetic film, the effective mean free pathof the ferromagnetic film is extended, and this makes it possible tofurther enhance the magnetoresistance effect of the spin valve typestacked film. If, however, the resistivity of the thin film is lowerthan that of the ferromagnetic film, a current flows mainly into thestacked thin film, weakening the magnetoresistance effect. For thisreason, the material of the thin film is required to have both a longmean free path and a specific resistance higher than that of theferromagnetic film.

In addition, when a material with a high resistivity is used as theabove thin film having a long mean free path, the specific resistance ofthe entire spin valve type stacked film can be raised by decreasing thethickness of the ferromagnetic film in contact with the thin film.Consequently, a spin valve type stacked film with a high specificresistance can be obtained, and this makes it possible to extract a highsignal voltage with a low current density even in a fine pattern.Therefore, problems such as generation of heat and migration can beavoided.

In the sixth aspect of the present invention, when a Co_(1-x) Fe_(x)(0<×<1) film as a ferromagnetic film is formed on a nonferromagneticfilm consisting of a material having the fcc phase and a latticeconstant larger than that of the material of the ferromagnetic film, aproper lattice strain is induced in the CoFe film, and consequently theHc decreases largely to achieve good soft magnetic characteristics. Byfurther forming a nonmagnetic film, such as a Cu film, anotherferromagnetic film having a spin-dependent scattering ability, such as aCoFe film, and an antiferromagnetic film in sequence on the aboveferromagnetic film, there can be provided a high-sensitivitymagnetoresistance effect element which produces a large resistancechange upon application of a slight signal magnetic field. In this case,if the resistivity of the nonferromagnetic film formed on a substrate ishigher than that of the ferromagnetic film, a sense current can beprevented from being shunted to this nonferromagnetic film, so a highresistance change rate results. In addition, if the smoothness in eachinterface suffers to decrease the resistance change rate because thenonferromagnetic film does not grow into layers, a high resistancechange rate can be realized by interposing another undercoating filmwith a function of growing a layered film between the nonferromagneticfilm and the substrate.

Furthermore, this lattice strain can be controlled easily by adjustingthe film thickness of the ferromagnetic film or the film thickness ofthe nonferromagnetic film as well as selecting the type of thenonferromagnetic film.

In the seventh aspect of the present :invention, a unit stacked filmconstituted by ferromagnetic films and a first nonmagnetic film has goodsoft magnetic characteristics and good lattice matching properties. Inaddition, in this unit stacked film, the resistance in the ferromagneticcoupled state is lower than that in the antiferromagnetic coupled state,and the number of interfaces causing spin-dependent scattering betweenthe ferromagnetic films and the nonmagnetic film is large. For thisreason, the increase in ΔR/R due to so-called bulk scattering in theunit stacked film can be expected. Therefore, an artificial lattice filmor a film with a spin valve structure using this unit stacked film as aferromagnetic film unit has good soft magnetic characteristics and showsa high resistance change rate derived from spin-dependent scattering.Consequently, a high-sensitivity magnetoresistance effect element can beobtained.

In the eighth aspect of the present invention, the magnetizationsbetween neighboring ferromagnetic films sharply change from anantiparallel state to a parallel state. In addition, a bias magneticfield from an antiferromagnetic film or the like required to obtain thisantiparallel state is suppressed to a minimum field necessary to preventBarkhausen noise. For this reason, even when a signal magnetic field isapplied in the direct log of the axis of hard magnetization suitable fora magnetic head (in this direction, an advantage such as good RFcharacteristics can be obtained), the magnetizations of the twoferromagnetic films rotate to change within the range of a relativelylow magnetic field of 0° to 180°. Therefore, a high resistance changerate equivalent to that obtained in the easy axis of magnetization canbe obtained within the range of a relatively low magnetic field.

In a conventional spin valve type magnetoresistance effect element, itis desirable that the thickness of a nonmagnetic layer be as small aspossible since the resistance change rate increases exponentially as thethickness of the nonmagnetic layer decreases. In practice, however, ifthe film thickness of the nonmagnetic film sandwiched betweenferromagnetic films is less than 2 nm, the ferromagnetic couplingbetween the upper and lower magnetic layers is enhanced to makerealization of an antiferromagnetic magnetization arrangementimpossible, and this largely decreases the resistance change rate. Inthe eighth invention of the present invention in which a bias magneticfield is applied to both the ferromagnetic films, however, theantiferromagnetic magnetization alignment can be realized by adjustingthe intensity of an antiparallel bias magnetic field even if thethickness of the nonmagnetic film is less than 2 nm. Therefore, a greatincrease in the resistance change rate can be expected.

In addition, the bias magnetic field is applied to all magnetic films.This removes domain walls from all the ferromagnetic films, therebypreventing Barkhausen noise.

Furthermore, in a system in which a sense current is flowed in adirection perpendicular to a signal magnetic field, the presentinvention can achieve both a conventional anisotropic magnetoresistanceeffect, which cannot be ignored when, e.g., an NiFe film is used, and aresistance change caused by spin-dependent scattering, and thisconsequently increases the ΔR/R.

In the ninth aspect of the present invention, assuming that the angledefined between the magnetization of a magnetization locking film andthe magnetization of a signal magnetic field detecting film is set atabout 90° when the signal magnetic field is 0, if the magnetization ofthe magnetization locking film points in the direction of a positivesignal magnetic field, the resistance decreases in the positive magneticfield since the angle defined between the magnetizations of theneighboring ferromagnetic films becomes ferromagnetic. In contrast, in anegative magnetic field, the resistance increases because the angledefined between the magnetizations of the neighboring ferromagneticfilms becomes antiferromagnetic. This consequently makes an operatingpoint bias unnecessary. Furthermore, the sense current is applied in thedirection of the signal magnetic field to lock the magnetization of atleast one ferromagnetic film in that direction by using theantiferromagnetic film or the like. The magnetization of the otherferromagnetic film whose magnetization is, thereby, not locked isinclined in a direction perpendicular to the signal magnetic field bythe current magnetic field. This current magnetic field achieves theeffect of preventing Barkhausen noise. In this case, the ferromagneticfilm whose magnetization is not locked need not have the axis of easymagnetization because of the presence of the current magnetic field.

In the tenth aspect, by inclining the angle defined between themagnetization locking and the signal magnetic field detecting film by30° to 60°, Barkhausen noise can be removed by a leakage magnetic fieldfrom the magnetization locking film while the operating point biasremains unnecessary.

When the sense current is flowed in a direction perpendicular to thesignal magnetic field, the direction of the ferromagnetically coupledmagnetic field and the direction of the current magnetic field arepresent on the same axis. If the sense current is flowed such that thedirection of the ferromagnetic coupling between the adjacentferromagnetic films, which cause a decrease in permeability issuperposed on the direction of this current magnetic field, themagnetization direction of the magnetic film whose magnetization is notlocked is rotated in the magnetization direction of the magnetic filmwhose magnetization is locked. Therefore, the angle defined between themagnetizations of the two magnetic films decreases from 90°, As aresult, even if a material having an anisotropic magnetoresistanceeffect is used, the sensitivity is increased effectively by thesuperposition of the anisotropic magnetoresistance effect and theresistance change derived from spin-dependent scattering (in this case,however, the range of the linear response magnetic field is narrowedwith respect to the signal magnetic field). If, in contrast, the sensecurrent is flowed such that the direction of the ferromagnetic couplingbecomes opposite to the direction of the current magnetic field, therange of the linear response magnetic field can be widened with respectto the signal magnetic field, since the angle defined between the twomagnetic layers can be set at about 0° when the signal magnetic field is0 (in this case, however, if an anisotropic magnetoresistance effectexists, this anisotropic magnetoresistance effect interferes with alinear resistance change obtained by spin-dependent scattering).

In the eleventh aspect of the present invention, two bias films areincorporated in the (magnetic film/nonmagnetic film)_(n) film. Thus, anintense bias magnetic field can be applied to specified ferromagneticfilms to lock them magnetically, and a minimum-intensity magnetic fieldcan be applied to other specified ferromagnetic films to remove bulkspin noise. Furthermore, a bias field can be applied to the signal fielddececting magnetic film by stacking magnetization-loked films on theedge of the signal field detecting magnetic film. As this method needsto remove the other films stacked on the signal field dececting film, itis difficult to fablicate such a structure. However, this method isadvantageous in that the multi-layer film including the bias films canbe formed within a short time by means of a continuous film-formingprocess. Furthermore, the two bias magnetic fields may be applied atright angles, in which case the angle defined between the magnetizationdirections of a magnetization locking film and a field detecting filmbecomes about 90° when the signal magnetic field is 0 as in the tenthaspect of the invention. This makes an operating point bias unnecessary.In addition, Barkhausen noise can be removed by a bias magnetic fieldapplied to the field detecting film. In this system, the magnitude ofthe bias magnetic field can be controlled easily by adjusting themagnetic anisotropy or the film thickness of a bias film to be stackedon the field detecting film or by adjusting the interface between thefield detecting film and the bias film.

In the twelfth aspect of the present invention, since the uppermost andlowermost ferromagnetic films have a low permeability, i.e., theirmagnetizations are locked, a change in magnetization with respect to asignal magnetic field is subtle. Since, on the other hand, thepermeability of an intermediate ferromagnetic film is high, a largerotation of magnetization takes place upon application of a slightmagnetic field. As a result, the angle defined between the magnetizationof the uppermost and lowermost ferromagnetlc films and the magnetizationof the intermediate ferromagnetic film changes sensitively in accordancewith the signal magnetic field. In addition, the number of interfacesfor causing spin-dependent scattering is at least twice that in aconventional spin valve type film. Therefore, a large change inresistance can be obtained by a slight magnetic field.

Note that if the permeability of the intermediate ferromagnetic film islowered by locking its magnetization by using an antiferromagnetic film,the ΔR/R decreases largely because the antiferromagnetic film has a highresistivity. In the uppermost and lowermost ferromagnetic films,however, locking of magnetization is possible without decreasing theΔR/R, since the antiferromagnetic film for locking magnetization can bearranged outside the unit of spin-dependent scattering.

Furthermore, because the ferromagnetic film with a high permeability ispresent in the vicinity of the center of the spin valve type stackedfilm, the magnetic field from the sense current is weak. Thisconsequently avoids a problem that the magnetization arrangement of theferromagnetic film is disturbed by the sense current magnetic field.

In the thirteenth aspect of the present invention, it is possible toprevent a normal high-coercive-force film from increasing the coerciveforce of a low-coercive-force film by using strong static couplingcaused by crystal magnetic anisotropy in a direction perpendicular tothe film surface. Therefore, when a magnetoresistance effect element ismanufactured by stacking at least two high-coercive-force films via amagnetoresistance effect film and an interlayer, the soft magneticcharacteristics of a film corresponding to a magnetization response arenot degraded. It is also possible to realize a parallel state and anantiparallel state of magnetizations efficiently, and to increase theresistance change rate since the film thickness of the interlayer can bedecreased significantly.

Furthermore, since the single-crystal-like high-coercive-force film hasa low electrical resistance, the output can be increased withoutadversely affecting spin-dependent scattering even when thishigh-coercive-force film is stacked on a low-coercive-force film. Thissingle-crystal-like high-coercive-force film also has a high crystalmagnetic anisotropy. Therefore, the film has a high permeability (i.e.,its magnetization is hard to move) and hence can achieve a largemagnetization locking effect.

Even when used as a bias film, the high-coercive-force film does notdegrade the soft magnetic characteristics of a film corresponding to amagnetization response. This bias film can be used as both a bias filmfor preventing Barkhausen noise and a bias film for obtaining ananticoupled state of magnetizations when no external magnetic field ispresent, i.e., can be imparted with the two effects at the same time.

The present invention will be described in more detail below by way ofits examples.

As regards the first to thirteenth aspects of the present invention, inthe case where there are a plurality of films in one structure, it isonly necessary that at least one of the films should satisfy the specs.

EXAMPLE 1

A sapphire substrate C face (the (0001) plane of an α-Al₂ O₃ substrate)was polished into a mirror surface by using a mechanochemical polishingprocess until the average surface roughness became about 2 nm whenmeasured by a probe type surface roughness meter with a probe radius of0.2 μm.

The resultant sapphire substrate was placed in a vacuum chamber, and thevacuum chamber was evacuated to 5×100⁻⁷ Torr or less. Thereafter, Ar gaswas introduced into the vacuum chamber to set a vacuum degree of about 3mTorr in the vacuum chamber, and sputtering was performed in a staticmagnetic field of about 4,000 A/m, thereby forming in sequence a Co₉₀Fe₁₀ film 11 as a ferromagnetic film, a Cu film 12 as an intermediatenonmagnetic film, another Co₉₀ Fe₁₀ film 11 as a ferromagnetic film, anFeMn film 13 as an antiferromagnetic film, and a Ti film 14 as aprotective film on the sapphire substrate 10, as shown in FIG. 3. As aresult, a stacked film with a spin valve structure of 5 nm Ti/8 nmFeMn/8 nm Co₉₀ Fe₁₀ /2.2 nm Cu/8 nm Co₉₀ Fe₁₀ was formed on the sapphiresubstrate 10, thereby manufacturing a magnetoresistance effect element.Cu leads 15 were also formed on this stacked film. Note that Co₉₀ Fe₁₀was used as the composition of the CoFe-based alloy film because Co₉₀Fe₁₀ has a high resistance change rate [Japan Applied Magnetics SocietyJournal, 16, 313 (1992)] and soft magnetic characteristics.

As the material of the protective film other than Ti, nonmagneticsubstances such as Cu, Co, W, SiN, and TiN can be used. To preventoxidation of FeMn, it is desirable to use a material other than oxides.The film thickness of the Ti film need not be 5 nm provided that thefilm maintains a protecting effect. In order to prevent a decrease insensitivity caused by a shunt current flowing to the Ti film when a;sense current is flowed, the film thickness is preferably several tensnm or less when the electrical resistivity of the Ti film higher thanthat of the Co₉₀ Fe₁₀ is taken into account.

The magnetization of the Co₉₀ Fe₁₀ film 11 in contact with the FeMn film13 is locked by the FeMn, and the magnetization of the other Co₉₀ Fe₁₀film 11 is reversed or rotated in accordance with an external magneticfield. The film thickness of both the Co₉₀ Fe₁₀ films 11 as theferromagnetic films was set to 8 nm, but the thicknesses of the twofilms may be the same or different. In principle, a ferromagnetic filmis usable if its thickness is one atomic layer (0.2 nm) or more.However, the thickness is suitably 0.5 to 20 nm when an actualapplication of an MR element is taken into consideration.

In this example, the film thickness of the Cu film 12 formed between thetwo Co₉₀ Fe₁₀ films 11 was 2.2 nm. However, the thickness is not limitedto this value and is preferably 0.5 to 20 nm in practice. As thematerial other than Cu, Au, Ag, Ru, and Cu alloy can be used.

The FeMn film 13 as the antiferromagnetic film is used to lock themagnetization of the Co₉₀ Fe₁₀ film 11 which the FeMn film 13 is indirect contact with. Although the FeMn film 13 was usable if its filmthickness was about 1 nm or more, the film thickness is desirably 2 to50 nm in respects of reliability and practicality. Note that Ni oxide isalso usable as the material of the antiferromagnetic film in addition toFeMn. When Ni oxide is used as the material of the antiferromagneticfilm, it is possible to form an antiferromagnetic film of the Ni oxidewith good properties by performing sputtering in a gas mixtureatmosphere of Ar and oxygen, or by applying an ion beam sputteringprocess or a dual ion beam sputtering process. In addition, since the Nioxide film can be formed well on the sapphire substrate C face, it ispossible to form a spin valve structure of 5 nm Ti/8 nm Co₉₀ Fe₁₀ /2.2mn Cu/8 nm Co₉₀ Fe₁₀ /50 nm Ni oxide. In this case, if the thickness ofthe Ni oxide film is 1 nm or more, a stable bias magnetic field can beapplied to the Co₉₀ Fe₁₀ film,

The magnetic characteristics, the resistance change rate, and thecrystal structure of the magnetoresistance effect element were examined.The magnetic characteristics were measured with a maximum appliedmagnetic field of 1.2 MA/m by using a vibrating magnetometer (VSM), andthe resistance change rate was measured in a static magnetic field inaccordance with a four-terminal resistance measurement method. Thecrystal structure was measured by θ-2θ scan and a rocking curve X-raydiffraction method. The measurements using the VSM and the X-raydiffraction were performed for a film patterned into squares of 8 mmside through a metal mask, and the resistance change rate was measuredfor a film patterned into stripes of 1 mm×8 mm through a metal mask. Thechange in resistance of the magnetoresistance effect element in amagnetic field was measured by the four-terminal method.

The measurement results of the magnetoresistance effect element areshown in FIG. 4. As can be seen from FIG. 4, when an external magneticfield was applied in the direction of the axis of easy magnetization,the maximum resistance change rate was approximately 10%. The coerciveforce of this magnetoresistance effect element was 160 A/m or less. Thatis, in this magnetoresistance effect element, a large resistance changeof about 10% was obtained for a weak magnetic field of about 160 A/m,indicating that good soft magnetic characteristics and a high resistancechange rate were obtained. In addition, when an external magnetic fieldwas applied in the direction of the axis of hard magnetization, althoughthe resistance change rate was about 4%, the coercive force was 80 A/m,i.e., the soft magnetic characteristics were very good.

The magnetization curves of this magnetoresistance effect element areshown in FIGS. 5A and 5B. As is apparent from FIG. 5A, the coerciveforce in the axis of easy magnetization was approximately 160 A/m, andthe coercive force in the axis of hard magnetization was about 80 A/m.In addition, as can be seen from FIG. 5B, an exchange bias of about 5.3kA/m was applied to the Co₉₀ Fe₁₀ film in contact with FeMn in thedirection of the axis of easy magnetization.

The crystal structure of this magnetoresistance effect element presenteda strong fcc-phase (111) orientation (closest packed plane orientation).

Following the same procedures as described above, Ti/FeMn/CoFe/Cu/CoFefilms were formed on a thermal oxide Si substrate, and thecharacteristics of the resultant structure were evaluated. As a result,the closest packed plane X-ray diffraction peak was decreased to 1/10 orless of the above value, and the Hc was 3000 A/m in the axis of easymagnetization, which is a high value inapplicable to a magnetoresistanceeffect element. The resistance change rate was about 8%, lower than thatof the above (111)-oriented film.

Subsequently, following the same procedures as described above,Ti/FeMn/CoFe/Cu/CoFe films were formed on an MgO (100) substrate, andthe characteristics of the resultant structure were evaluated.Consequently, the X-ray diffraction peak exhibited only ahigh-intensity, (100) peak, indicating a good (100) orientation. At thistime, however, the Hc in the axis of easy magnetization was 1,200 A/m,i.e., presented a high value inapplicable to a magnetoresistance effectelement. The resistance change rate was approximately 8%, lower thanthat of the above (111)-oriented film.

The above evaluation results show that realization of the (111)orientation can achieve a low Hc and a high resistance change rate atthe same time.

Subsequently, a magnetoresistance effect element with a spin valvestructure of 5 nm Ti/8 nm FeMn/8 nm Co/2.2 nm Cu/8 nm Co using Co filmsas ferromagnetic films was formed on a sapphire C face substrate, andthe magnetic characteristics and the resistance change rate of theresultant magnetoresistance effect element were measured following thesame procedures as described above. Consequently, this magnetoresistanceeffect element showed the closest packed plane orientation similar tothat described above, a resistance change rate of about 8%, and acoercive force of about 1600 A/m. Note that ΔR/R=7% and Hc=2,000 A/mwhen a thermal oxide Si substrate was used.

The above results reveal that although a low Hc and a high ΔR/R can beobtained by using Co as the material of the ferromagnetic film, it ismore preferable to use an alloy formed by adding Fe to Co as thematerial of the ferromagnetic film because soft magnetic characteristicscan be obtained more easily.

Spin value type magnetoresistance effect elements having a structure of5 nm Ti/8 nm FeMn/8 nm Co_(1-x) Fe_(x) /2.2 nm Cu/8 nm Co_(1-x) Fe_(x)/sapphire C face or glass substrate were prepared at variation valuesfor the parameter X of Fe content Co_(1-x) Fe_(x) ferromagnetic film.The relationship ΔR/R and Hc thus obtained are summarized in Table 6.

                  TABLE 6                                                         ______________________________________                                        X      substrate      Hc(A/m)  ΔR/R(%)                                  ______________________________________                                        0.05   sapphire C face                                                                               400     9.5                                            0.10   "               160     10                                             0.15   "               240     12                                             0.20   "               420     11                                             0.30   "               400     10.5                                           0.40   "               700     9                                              0.60   "              2200     6                                              0.05   glass          2800     7.5                                            0.10   "              3000     8                                              0.15   "              1800     7.5                                            0.20   "              1500     7                                              0.30   "              1700     7                                              0.40   "              2500     7.5                                            0.60   "              3000     6                                              ______________________________________                                    

As is clear from Table 6, a decrease in Hc and an increase in ΔR/R wereobserved on the sapphire C face within a range of 0.05≦×≦0.4.

EXAMPLE 2

As shown in FIG. 6, Co₉₀ Fe₁₀ films 21 and Cu films 22 were stackedalternately 16 times on the C face of a sapphire substrate 20 under thesame film formation conditions as in Example 1, and a Cu film 23 wasformed on the resultant structure, thereby manufacturing an artificiallattice film with a structure of 5.5 nm Cu/(2 nm Cu/1 nm Co₉₀ Fe₁₀) ×16to obtain a magnetoresistance effect element. Cu leads 24 were alsoformed on this stacked film.

The field dependency of the resistance change rate of thismagnetoresistance effect element was measured. The results are shown inFIG. 7. As shown in FIG. 7, the maximum resistance change rate wasapproximately 20%, the saturation magnetic field was about 2,400 A/m,and the coercive force was 160 A/m. These results show that a largechange in magnetic resistance of about 20% could be obtained by arelatively weak magnetic field of 2,400 A/m.

It was also possible to obtain a resistance change rate of 10% or moreeven when the film thickness of the Co₉₀ Fe₁₀ films was changed from 0.5to 3 nm in the above structure. In addition, even when the stackingorder of the Co₉₀ Fe₁₀ films 21 and the Cu films 22 was reversed, i.e.,the Cu films 22 and the Co₉₀ Fe₁₀ films 21 were stacked alternately inthis order, the crystal structure presented a strong fcc-phase (111)orientation like in the case of the spin valve structure of Example 1.

EXAMPLE 3

A 10-nm thick Cu undercoating film was formed on each of the C face of asapphire substrate, a glass substrate (#0211 available from CorningGlass Works), and the (111) plane of an Si substrate. A Co₉₀ Fe₁₀ filmwas formed on each resultant structure under the same film formationconditions as in Example 1. Note that the Cu undercoating film can beformed by a bias sputtering process or an ion-assisted ion beamsputtering process or vapor deposition process. The coercive force (Hc)of each Co₉₀ Fe₁₀ film was measured. In addition, Co₉₀ Fe₁₀ films withdifferent film thicknesses were formed on the individual substrates viathe Cu undercoating films, and the coercive forces (Hc) of these Co₉₀Fe₁₀ films were measured. The results are shown in FIG. 8. Furthermore,Co₉₀ Fe₁₀ films with different film thicknesses were formed on theindividual substrates without forming any Cu undercoating film followingthe same procedures as described above, and the coercive forces (Hc) ofthese films were measured. The results are shown in FIG. 9.

It is obvious from FIGS. 8 and 9 that in any of these substrates, the Hcwhen the Cu undercoating film was formed (FIG. 8) was lower than thatwhen a Cu undercoating film was not formed. FIGS. 8 and 9 also revealthat the Hc decreased in an order of the C face of the sapphiresubstrate, the (111) plane of the Si substrate, and the glass substrate,i.e., the Hc became better in this order, regardless of thepresence/absence of the Cu undercoating film. Especially when a Co₉₀Fe₁₀ film 8 nm in thickness was formed on the C face of the sapphiresubstrate, a low Hc of 80 A/m or less was obtained. The Hc of the Co₉₀Fe₁₀ film with the Cu undercoating film tended to increase slightly asthe film thickness of the Co₉₀ Fe₁₀ film increased. When a Cuundercoating film was not formed, on the other hand, the Hc of the Co₉₀Fe₁₀ film tended to decrease with an increase in film thickness at firstand then increased as the film thickness increased further. As anexample, when the film thickness of the Co₉₀ Fe₁₀ film was about 8 nm,the minimum value of the Hc of that film was 160 A/m or less.

The above outcomes indicate that good soft magnetic characteristics canbe obtained by forming an undercoating film between a substrate and aferromagnetic film.

It is also found that good soft magnetic characteristics can be obtainedby using a CuNi alloy film as an undercoating film when a Co₉₀ Fe₁₀ filmor a Co film is formed on the C face of a sapphire substrate or an Sisubstrate. In addition, it is found that the use of a Ge, Si, or Ti filmwith a thickness of about a few nm to 100 nm as an undercoating filmwhen a Co₉₀ Fe₁₀ film or a Co film is formed on a glass substrate or aceramic substrate promotes closest packed plane orientation, andconsequently good soft magnetic characteristics can be obtained.

It is also possible to prevent a shunt current of an MR sense current byforming an undercoating film consisting of a material with a higherresistance than that of a Co₉₀ Fe₁₀ film or a Co film. For example, theNi oxide film described in Example 1 is an antiferromagnetic film thathas a high resistance and can be epitaxially grown on the C face of asapphire substrate. Therefore, this Ni oxide film can serve as both anundercoating film and an antiferromagnetic bias film. FIG. 10illustrates a magnetoresistance effect element with a spin valvestructure using an Ni oxide film 26.

EXAMPLE 4

The influence that the plane orientation of a sapphire substrate has onthe coercive force of a Co₉₀ Fe₁₀ film was examined. In this example,comparison was made between the C face and the R plane (the (1012) planeof an α-Al₂ O₃ substrate).

A 10-nm thick Co₉₀ Fe₁₀ film was formed on each of the C face and the Rplane of a sapphire substrate. FIGS. 11A and 11B show the difference incrystal orientation derived from this plane orientation. As is apparentfrom FIG. 11A, a good fcc (111) orientation was realized on the C face,and it was consequently possible to form a CoFe alloy film having goodsoft magnetic characteristics with a coercive force of 160 A/m or less.FIG. 11B, on the other hand, reveals that a peak of fcc (200) was foundin addition to a peak of fcc (111) on the R plane, indicating that thefcc (111) orientation was not so good. For this reason, the coerciveforce was several hundreds A/m or more, i.e., no good soft magneticcharacteristics could be obtained.

Referring to FIG. 11A, only a peak (which may contain a slight hcp-phase(001) orientation) corresponding to the fcc-phase (111) plane stronglyappears near 2θ=43.5° on the C face in addition to the peak of sapphireas the substrate. The higher this peak intensity, the lower the coerciveforce of the Co₉₀ Fe₁₀ film. Referring to FIG. 11B, on the other hand, apeak corresponding to the fcc-phase (200) plane appears near 2θ=52.6° onthe R plane in addition to the peak of sapphire and the fcc-phase (111)plane peak. The presence of this fcc-phase (100) orientation meansappearance of an axis of easy crystal magnetic anisotropy in the plane,and this causes an increase in coercive force.

Subsequently, a rocking curve was measured for the peak corresponding tothe (111) plane (closest packed plane) of the Co₉₀ Fe₁₀ film on the Cface of the sapphire substrate. FIG. 12 shows this rocking curve. As canbe seen from FIG. 12, a very strong orientation with a half-width ofabout 3° is found around a peak near θ=21.8°. Although the peak of thesapphire substrate also overlaps on this rocking curve, a good crystalorientation of the Co₉₀ Fe₁₀ film is found.

FIG. 13 shows the correlation between the coercive force of the Co₉₀Fe₁₀ film and the half-width of the rocking curve at a peakcorresponding to the (111) plane (closest packed plane) of the Co₉₀ Fe₁₀film. It is clear from FIG. 13 that when a Co₉₀ Fe₁₀ film was formed ona glass substrate, the (111) peak was often weak, the rocking curvehalf-width was 20° or more, and the Hc was 3,000 A/m or more. The Hcdecreased to about 1,000 A/m when the half-width of the rocking curvewas decreased to about 15° by optimizing the Ar pressure and thesubstrate temperature. When a film consisting of a material prepared byadding about 1% of Al to this Co₉₀ Fe₁₀ was formed on a glass substrate,the half-width decreased to approximately 8°, decreasing the Hc to about350 A/m. When a Co₉₀ Fe₁₀ film was formed on the C face of a sapphiresubstrate, the half-width further decreased to about 3°, decreasing theHc to about 160 A/m. It was therefore confirmed that as the half-widthof the rocking curve of the peak corresponding to the closest packedplane (the (111) plane in the case of the Co₉₀ Fe₁₀ film) decreased toless than 20°, the coercive force tended to decrease abruptly. Forexample, the coercive force approached a good value, 160 A/m, when thehalf-width of the rocking curve was 7° or less. That is, as the closestpacked plane orientation of the Co₉₀ Fe₁₀ film was enhanced, thecoercive force of the Co₉₀ Fe₁₀ film was decreased. This indicates thatthere is a strong correlation between good soft magnetic characteristicsand the orientation of a ferromagnetic film.

A method of enhancing the closest packed plane orientation of the Co₉₀Fe₁₀ film can be selected from 1) a method of adding various additiveelements (to be described later), 2) a method of selecting the materialand the orientation of a substrate (e.g., selecting the C plane of asapphire substrate), 3) a method of forming an undercoating filmconsisting of any of Ti, NiO, a metal with an fcc structure, a metalwith a diamond structure such as Si or Ge, a metal with a zinc-blendestructure such as GaAs, or an amorphous metal between a substrate andthe Co₉₀ Fe₁₀ film, and 4) a method of performing film formation byusing an ultra-high vacuum film formation apparatus such as MBE. Notethat when the C face of a sapphire substrate was used as a substrate inthe above second method, the Co₉₀ Fe₁₀ film formed on that C faceexhibited better soft magnetic characteristics by setting the meansurface roughness (Ra) of the substrate to 2 nm or less by polishing theC face by means of mechanochemical polish, float polish, or ion polish.If, however, the mean surface roughness was 5 nm or more, the coerciveforce of the Co₉₀ Fe₁₀ film was 1,000 A/m or more.

EXAMPLE 5

It is found in Example 4 that the coercive force of a single-layeredCo₉₀ Fe₁₀ film is decreased by enhancing the closest packed planeorientation in accordance with the first or second method. In Example 5,whether the same applies to a stacked film containing a Co₉₀ Fe₁₀ filmis confirmed.

A stacked film with a structure of 10 nm Al-containing Co₉₀ Fe₁₀ /5 nmCu/10 nm Al-containing Co₉₀ Fe₁₀ was formed on a glass substrate underthe same film formation conditions as in Example 1. FIG. 14 shows therelationship between the Al element addition amount in the Co₉₀ Fe₁₀film and the coercive force of the Co₉₀ Fe₁₀ film. As shown in FIG. 14,the coercive force could be decreased by the addition of the Al elementeven in the stacked film. It was also possible to similarly enhance theclosest packed plane orientation of the Co₉₀ Fe₁₀ film in the stackedfilm in accordance with the second to fourth methods described inExample 4.

FIG. 15 shows the closest packed plane peak intensity dependency of thecoercive force of the Co₉₀ Fe₁₀ film in the stacked film. As is clearfrom FIG. 15, the coercive force decreased as the closest packed planepeak intensity increased like in the single-layered film. In the abovestructure, the peak intensity was weak, 10² (a.u.), and the coerciveforce was approximately 10³ A/m. In this case, the coercive force wasdecreased to about several hundreds A/m by the use of a film consistingof a material formed by adding about 1% of Al to Co₉₀ Fe₁₀. In addition,by replacing the glass substrate with the C face of a sapphiresubstrate, a peak intensity of 10³ (a.u.) or more and a good coerciveforce of 100 A/m or less could be obtained. At this point, thehalf-width was 7° or less.

EXAMPLE 6

A coercive force was checked by adding elements other than Al to Co₉₀Fe₁₀. Consequently, a decrease in coercive force was found when Ta, Pd,Zr, Hf, Mo, Ti, Nb, Cu, Rh, Re, In, B, Ru, Ir, and W were used as theadditive elements. The coercive force was also decreased whencombinations of these elements, such as Ta and Pd, Nb and Pd, and zr andNb, were added. As an example, FIG. 16 shows the relationship betweenthe addition amount of Ta and the coercive force in a stacked film witha structure of 10 nm Ta-containing Co₉₀ Fe₁₀ /5 nm Cu/10 nmTa-containing Co₉₀ Fe₁₀. It is clear from FIG. 16 that the coerciveforce was decreased upon addition of the Ta element.

EXAMPLE 7

In each of the above examples, the high (111) orientation was realizedfor the CoFe film. However, the same effect was found when a CoFeNi filmand a CoNi film were used. This example is shown in Table 1 below. Table1 shows (1) the composition of a ferromagnetic film, (2) the type of asubstrate, and (3) the half-width Δθ₅₀ of a rocking curve at a (111)peak, the Hc in the axis of easy magnetization, and the ΔR/R of a spinvalve film having a structure (in which a CoFe film with no addictiveelements was formed on the side in contact with an FeMn film) similar tothat shown in FIG. 3, which was manufactured by using, as a parameter,an undercoating film formed between a substrate and the spin valve film.For comparison, the results obtained when spin valve films usingferromagnetic films with the same compositions as in Table 1 weremanufactured on glass substrates without forming any undercoating filmsare also shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                          Under-                                                                        coating  Δθ.sub.50                                                                 Hc    ΔR/R                           Composition                                                                            Substrate                                                                              film     (°)                                                                            (A/m) (%)                                  ______________________________________                                        Co.sub.20 Ni.sub.80                                                                    Glass    None     20 or more                                                                            680   5.5                                  Co.sub.20 Ni.sub.80                                                                    Sapphire None     3.8     440   5.9                                           C face                                                               Co.sub.20 Ni.sub.80                                                                    Glass    Ti10 nm  6.5     240   5.0                                  Co.sub.20 Ni.sub.80                                                                    Glass    Ge15 nm  4.1     190   5.8                                  Co.sub.20 Ni.sub.80                                                                    Glass    Si14 nm  5.8     210   5.8                                  Co.sub.20 Fe.sub.15 Ni.sub.65                                                          Glass    None     20 or more                                                                            270   6.1                                  Co.sub.20 Fe.sub.15 Ni.sub.65                                                          Sapphire None     4.8     210   6.9                                           C face                                                               Co.sub.20 Fe.sub.15 Ni.sub.65                                                          Glass    Ti 7 nm  6.7     120   5.8                                  Co.sub.20 Fe.sub.15 Ni.sub.65                                                          Glass    Ge15 nm  5.3      70   6.8                                  Co.sub.20 Fe.sub.15 Ni.sub.65                                                          Glass    Si14 nm  5.5      90   6.2                                  Co.sub.90 Fe.sub.10                                                                    Glass    None     20 or more                                                                            3500  8.0                                  Co.sub.90 Fe.sub.10                                                                    Glass    Ti10 nm  9.1     400   6.9                                  Co.sub.90 Fe.sub.10                                                                    Glass    Ge15 nm  6.0     210   8.6                                  Co.sub.90 Fe.sub.10                                                                    Glass    Si14 nm  5.8     190   7.1                                  ______________________________________                                    

As can be seen from Table 1, even when the CoFeNi film or the CoNi filmrather than the CoFe film was used, by using the sapphire C facesubstrate or by forming the undercoating film consisting of Ti, Si, orGe, a good (111)-oriented film with Δθ₅₀ <7° could be obtained. As aresult of this, the Hc was decreased, and the resistance change rate wasincreased as compared with the case wherein film formation was performeddirectly on the glass substrate.

When, however, a (1-nm thick M/1-nm thick Cu)₁₆ artificial lattice filmwith a high (111) orientation (M: Co₂₀ Ni₈₀, Co₂₀ Fe₁₅ Ni₆₅) wasmanufactured by using an undercoating film consisting of Ti or using asapphire C face substrate, the ΔR/R showed a significantly small valueof 2% or less, and a high saturation magnetic field inherent inRKKY-like antiferromagnetic coupling disappeared. This indicates thatthe resistance change rate decreased because no RKKY-likeantiferromagnetic coupling could be obtained by the (111) orientation.Therefore, when a high (111) orientation is realized by a stacked filmof a type not using RKKY-like antiferromagnetic coupling (a so-callednoncoupled artificial lattice film (The 14th Japan Applied MagneticsSociety Science Lecture Summaries, 1990, page 177)) as well as the spinvalve film, both a high resistance change rate and a good soft magnetismcan be obtained easily.

It was also confirmed that the same effect could be obtained when theferromagnetic film in contact with FeMn was replaced with a film withthe same composition as that of the underlying magnetic film.

EXAMPLE 8

Following the same procedures as in Example 1, a spin valve film with astructure of 5 nm Ti/8 nm FeMn/8 nm CoFe/2.2 nm Cu/8 nm magnetic filmwas formed on a glass substrate (with no undercoating film). Table 2shows the relationship between the nonmagnetic additive element to beadded to the underlying magnetic film, the resistance change rate in theaxis of easy magnetization, and the Hc.

                  TABLE 2                                                         ______________________________________                                                       Resistance change                                                             rate (%) (in the                                                              axis of easy                                                   Composition    magnetiziation)                                                                            Hc (A/m)                                          ______________________________________                                        Co.sub.89.2 Fe.sub.9.8 Al.sub.1.0                                                            8.5          320                                               Co.sub.89.0 Fe.sub.9.0 Al.sub.2.0                                                            7.7           70                                               Co.sub.87.3 Fe.sub.7.7 Al.sub.5.0                                                            5.1           60                                               Co.sub.86.2 Fe.sub.7.3 Al.sub.6.5                                                            2.9          100                                               Co.sub.86 Fe.sub.7 Re.sub.7                                                                  6.7          180                                               Co.sub.87 Fe.sub.6 Zr.sub.7                                                                  6.1          120                                               Co.sub.87 Fe.sub.7 Ta.sub.6                                                                  5.5          120                                               Co.sub.81 Fe.sub.9 Ta.sub.10                                                                 1.5           95                                               Co.sub.83 Fe.sub.10 Hf.sub.7                                                                 6.8          230                                               Co.sub.79 Fe.sub.8 Pd.sub.13                                                                 8.8          2050                                              Co.sub.85 Fe.sub.7 Pd.sub.8                                                                  8.0          1700                                              Co.sub.78 Fe.sub.7 Cu.sub.15                                                                 7.9          380                                               Co.sub.75 Fe.sub.7 Pd.sub.9 Cu.sub.9                                                         7.7          440                                               Co.sub.17 Fe.sub.13 Ni.sub.57 Pd.sub.13                                                      5.5          180                                               Co.sub.19 Fe.sub.14 Ni.sub.60 Pd.sub.7                                                       5.9          180                                               Co.sub.16 Fe.sub.12 Ni.sub.55 Pd.sub.9 Cu.sub.8                                              5.3           80                                               Co.sub.17 Fe.sub.13 Ni.sub.59 Hf.sub.11                                                      5.0          120                                               Co.sub.19 Fe.sub.15 Ni.sub.60 Hf.sub.6                                                       5.7          120                                               Co.sub.81 Fe.sub.9 Au.sub.10                                                                 7.5          410                                               Co.sub.83 Fe.sub.10 Ag.sub.7                                                                 7.6          350                                               Co.sub.55 Fe.sub.5 Pd.sub.40                                                                 7.3          800                                               Co.sub.55 Fe.sub.5 Cu.sub.40                                                                 7.0          280                                               ______________________________________                                    

As is apparent from Table 2, the Hc was decreased compared with thefilms formed on the glass substrates by adding no nonmagnetic element.The decrease in Hc was significant upon addition of Al and Ta, but theresistance change rate largely decreased when large amounts of theseelements were added. It is clear from Table 2 that both a resistancechange rate of 5% or more, which exceeds the resistance change rateobtained by the spin valve film consisting of NiFe, and a low Hc can beachieved by less than 6.5 at % of Al or less than 10 at % of Ta. When Alor Ta was added to CoFe, the closest packed plane peak intensityincreased in X-ray diffraction. It is assumed that this decrease in Hcwas caused by the improvement in the crystal orientation described abovewhich was due to the improvement in the closest packed plane peakintensity in the x-ray diffraction obtained by the additive elements. Inaddition, there is a possibility that the decrease in the crystalmagnetic anisotropy upon addition of the elements also contributed tothe decrease in Hc. On the other hand, the Hc decreasing effect of Cu,Au, Ag or Pd was not so remarkable as that of Al or Ta. However, nodecrease in the resistance change rate was found even upon addition of alarge amount of 40 at % or less of those elements. The closest packedplane peak intensity in the X-ray diffraction also increased when Cu,Au, Ag or Pd was added to CoFe.

The corrosion resistance of each single-layered magnetic film (thickness100 nm) was checked by leaving the film to stand in a thermo-hygrostatat 65° C. and RH 95% for 100 hours. Consequently, although no colorchange was found in the films added with 7 at % or more of Pd, colorchanges were observed in the CoFe film with no nonmagnetic addictiveelements, the Co₂₀ Ni₈₀ film, the Co₂₀ Fe₁₅ Ni₆₅ film, the film whichwas added with 6.5 at % of Al, and the film which as added with 6 at %of Ta. That is, the addition of Pd achieves the effect of improving thecorrosion resistance. The decrease in Hc was not significant uponaddition of Pd alone. However, when Pd was added together with, e.g.,Cu, it was possible to further improve the soft magnetism whilemaintaining a high resistance change rate and a high corrosionresistance. When a sapphire substrate, an amorphous metal undercoatingfilm, or a fcc-lattice undercoating film was used, Hc (<80 A/m) wasreduced even by adding Pd only, and the resistance change rate increasedup to 10% by adding Pd in an amount of 40 at % at most. When, however,Pt which is also a noble metal and therefore expected to be effective inimproving the corrosion resistance was added, the Hc increased to behigher than those of films not added with Pt. For this reason, additionof Pt is unpreferable in respect of the soft magnetism.

EXAMPLE 9

After the surface of a thermal oxide Si substrate with surface roughnessR_(a) =2 nm or less was cleaned by SH mixture of sulfuric acid and H₂ O₂processing, the substrate was placed in a vacuum chamber, and thechamber was evacuated to 1×10⁻⁹ Torr or less. Water and oxygen in thevacuum chamber were controlled by a mechanical spectrometer and a dewpoint meter. After the above procedure, super-high-purity Ar gas wasintroduced into the vacuum chamber, and the vacuum degree in the chamberwas set at 1×10⁻⁴ Torr. Sputtering was then performed by using an ionbeam accelerated by generating microwave discharge of 2.45 GHz inside anECR ion source, thereby forming an amorphous Si film with a filmthickness of 5 nm as a first undercoating film 151 on the thermal oxideSi substrate 150 as shown in FIG. 17. Thereafter, while the vacuum inthe chamber was held, a Cu-Ni alloy film with a film thickness of 2 nmwas formed as a second undercoating film 152 on the first undercoatingfilm 151.

On the surface of the resultant structure, an 8-nm thick Co₉₀ Fe₁₀ alloyfilm as a first ferromagnetic film 153, a 2.2-nm thick Cu-Ni alloy filmas a nonmagnetic film 154, an 8-nm thick Co₉₀ Fe₁₀ alloy film as asecond ferromagnetic film 155, an 8-nm thick Fe-Mn alloy film as anantiferromagnetic film 156, and a 5-nm thick Ti film as a protectivefilm 157 were formed in sequence, manufacturing a stacked film with aspin valve structure. All of these thin films were formed by ion beamsputtering. Cu electrodes 158a and 158b were also formed on this stackedfilm to obtain a spin valve type magnetoresistance effect element 159.

Note that Co₉₀ Fe₁₀ was used as the composition of the Co-Fe alloy filmsas the ferromagnetic films 153 and 155 in respects of a high resistancechange rate (Japan Applied Magnetics Society Journal: 16. 313 (1992))and soft magnetic characteristics.

The crystallinity, the magnetic characteristics, and the resistancechange rate of the spin valve type magnetoresistance effect element thusmanufactured were measured. Consequently, the half-width of the Co-Fealloy film obtained by X-ray diffraction was 1°, and the coercive forceas one physical characteristic indicating soft magnetic characteristicswas 0.1 Oe. The rate of change in magnetic resistance measured by usingthis element exhibited a high value of approximately 10%.

As a comparison with this invention, a substrate subjected to the sameprocessing was placed in a vacuum chamber, and the chamber was evacuatedto 1×10⁻⁷ Torr or less. Thereafter, regular Ar gas was introduced intothe chamber until the vacuum degree became 2×10⁻³ Torr, and a Cu film asan undercoating film was formed directly on the surface of the substratewithout forming any amorphous Si film. Subsequently, a stacked film withthe same spin valve structure as that of Example 9 was formed on thesurface of the resultant structure. Cu electrodes were then formed onthis stacked film, thereby manufacturing a magnetoresistance effectelement. The stacked film was formed by a double-pole sputtering processexcited with a normal frequency of 13.56 MHz.

The crystallinity, the magnetic characteristics, and the resistancechange rate of this magnetoresistance effect element as the comparativeexample were measured. As a result, the half-width of the Co-Fe alloyfilm measured by X-ray diffraction was 7°, and the coercive force as onephysical characteristic indicating soft magnetic characteristics wasfound to be 1.5 Oe. The rate of change in magnetic resistance measuredby using this element was about 5%.

EXAMPLE 10

After the surface of a sapphire substrate with surface roughness R_(a)=2 nm or less was cleaned, the substrate was placed in a vacuum chamber,and the chamber was evacuated to 1×10⁻⁹ Torr or less. Water and oxygenin the vacuum chamber were controlled by using a mechanical spectrometerand a dew point meter. After the above procedure, an amorphous Cu-Tifilm with a film thickness of 3 nm was formed as a first undercoatingfilm by an ultra-high-vacuum vapor deposition process using an electronbeam vapor deposition source. Thereafter, while the vacuum in the vacuumchamber was maintained, an Fe-Mn alloy film with a film thickness of 2nm was formed as a second undercoating film by using ultra-high-vacuumRF sputtering at an excitation frequency of 100 MHz.

Subsequently, on the above undercoating films, constituent films of astacked film with a spin valve structure of 8 nm (Co₈₁ Fe₉ Pd₁₀)/5 nmTi/7 nm FeMn/2.2 nm Cu/8 nm (Co₈₁ Fe₉ Pd₁₀) were formed by usingultra-high-vacuum RF sputtering at an excitation frequency of 100 MHz.Cu electrodes were then formed on this stacked film, therebymanufacturing a spin valve type magnetoresistance effect element.

The crystallinity, the magnetic characteristics, and the resistancechange rate of the spin valve type magnetoresistance effect element thusmanufactured were measured following the same procedures as in Example9. Consequently, the half-width of the Co-Fe film measured by X-raydiffraction was 1.5°, and the coercive force as one physicalcharacteristic indicating soft magnetic characteristics was 1 Oe. Therate of change in magnetic resistance measured by using this element wasfound to be a high value of approximately 12%.

EXAMPLE 11

As shown in FIG. 18, a high-resistance amorphous layer 31 consisting ofCoZrNb was formed on a support substrate 30, and a ferromagnetic film 32consisting of a CoFe alloy, an interlayer 33 consisting of Cu, anotherferromagnetic film 32, and an exchange bias layer 34 consisting of FeMnwere formed in sequence on the high-resistance amorphous layer 31 in astatic magnetic field of about 4 kA/m. Thereafter, leads 35 were formedon the exchange bias layer 34, manufacturing a magnetoresistance effectelement. Note that the individual layers were formed under the filmformation conditions shown in Table 3 below by using a four-elementsputtering apparatus.

                  TABLE 3                                                         ______________________________________                                        Film Formation Conditions                                                                    Ferro-             Exchange                                    Amorphous      magnetic  Inter-   bias                                        layer          film      layer    layer                                       ______________________________________                                        Target  CoZrNb     CoFe      Cu     FeMn                                      Ultimate                                                                              8 × 10.sup.-5 Pa                                                vacuum                                                                        Sputter 0.4 Pa                                                                pressure                                                                      Supply  400 W      300 W     80 W   300 W                                     power                                                                         Film    10 nm      8 nm      3 nm   140 nm                                    thickness                                                                     ______________________________________                                         The film thickness of CoFe in contact with FeMn was 4.5 nm.              

The magnetic characteristics of this magnetoresistance effect elementwere examined. FIGS. 19 and 20 show the resultant M-H curves(magnetization-magnetic field curves). FIG. 19 shows the M-H curves inthe direction of the axis of easy magnetization, and FIG. 20 shows theM-H curves in the direction of the axis of hard magnetization.

As can be seen from FIG. 19, the coercive force Hc (indicated by a inFIG. 19) of the CoFe film not locked to FeMn was approximately 500 A/m,which was much smaller than Hc of about 1,600 A/m of a normal CoFesingle-layered film. In addition, as shown in FIG. 20, the coerciveforce Hc (indicated by b in FIG. 20) of the CoFe film not locked to FeMnwas about 600 A/m in the axis of hard magnetization on the signalmagnetic field input side. This value was also much smaller than the Hcof about 1,600 A/m of a regular CoFe single-layered film.

The resistance change characteristics of the magnetoresistance effectelement were also checked. FIG. 21 shows the resultant R-H curves(resistance-magnetic field curves). As shown in FIG. 21, the resistancechange rate ΔR/R exhibited a high value, about 9%, which was equivalentto that of a conventional Co-based spin valve film. The coercive forceHc (indicated by c in FIG. 21) of the CoFe film not locked to FeMn waslow, approximately 500 A/m, as can be predicted from FIG. 19.

Although the FeMn film was used as the exchange bias layer in thisexample, an antiferromagnetic film consisting of, e.g., NiO can also beused. It was also confirmed that good characteristics could be obtainedby using an artificial lattice film with a structure of, e.g.,(Co/Cu)_(n). In addition, the CoZrNb film was used as thehigh-resistance amorphous film in this example, but it is also possibleto use an FeZr film, an FeZrN film, a CoZrN film, an FeTaC film, or anNiFeX film (X: Rh, Nb, Zr, Hf, Ta, Re, It, Pd, Pt, Cu, Mo, Mn, W, Ti,Cr, Au, or Ag) consisting of fine crystals. In a fcc-phase fine crystalfilm (Co-based nitride, Co-based carbide or NiFeX film) in particular,not only was the fcc-phase (111) orientation promoted, but also did Hcdecrease (to 250 A/m in the axis of easy magnetization) and theresistance change rate increase to 10%.

For comparison, a ferromagnetic film, an interlayer, anotherferromagnetic film, and an exchange bias layer similar to those shown inFIG. 25 (to be described later) were formed in sequence on a supportsubstrate having no high-resistance amorphous layer, therebymanufacturing a magnetoresistance effect element. Thereafter, themagnetic characteristics of this magnetoresistance effect element wereexamined. FIGS. 22 and 23 show the resultant M-H curves. FIG. 22 showsthe M-H curves in the direction of the axis of easy magnetization, andFIG. 23 shows the M-H curves in the direction of the axis of hardmagnetization. The film formation conditions were the same as in Table3.

As is apparent from FIG. 22, the coercive force Hc (indicated by d inFIG. 22) of the CoFe film not locked to FeMn was about 2,000 A/m, whichwas a high value equivalent to that of a conventional CoFesingle-layered film. In addition, as shown in FIG. 23, the coerciveforce Hc (indicated by e in FIG. 23) of the CoFe film not locked to FeMnwas approximately 1,400 A/m in the axis of hard magnetization. Thisvalue was as high as the Hc of a normal CoFe single-layered film andhence unsatisfactory as the Hc of a magnetoresistance effect element.

EXAMPLE 12

As shown in FIG. 24, an undercoating film 36 about 5 nm in thicknessconsisting of Cu was formed on a support substrate 30, and an exchangebias layer 34, a ferromagnetic film 32, an interlayer 33, anotherferromagnetic layer 32, and a high-resistance amorphous layer 31 wereformed in sequence on the undercoating film 36. Leads 35 were thenformed on the high-resistance amorphous layer 31, thereby manufacturinga magnetoresistance effect element. Note that the film formationconditions were the same as shown in Table 3.

It was possible to obtain a low Hc even in the structure shown in FIG.24 in which the high-resistance amorphous layer was formed above theexchange bias layer. In addition, since the amorphous layer had a highresistance, no decrease in the rate of change in magnetic resistance wascaused by a shunt effect although this layer was formed as the uppermostlayer. In this structure, it is desirable to form the undercoating filmin order to control the crystal orientation of FeMn.

EXAMPLE 13

A CoPtCr film 42 was formed to have a thickness of 8 nm on a supportsubstrate 41, and a resist 43 was coated on the film 42. Thereafter, theresist 43 was patterned into a desired shape, and, as shown in FIG. 25A,etching was performed by ion milling. In this case, it is desirable thatthe taper angle X of CoPtCr be closer to 90°.

Subsequently, as shown in FIG. 25B, without removing the resist 43 afterthe etching, a ferromagnetic film 44 consisting of a CoFe alloy, aninterlayer 45 consisting of Cu, another ferromagnetic film 44, and ahigh-resistance amorphous layer 46 were formed in sequence,manufacturing a magnetoresistance effect element with a spin valvestructure. In this case, the taper angle Y of the resist 43 ispreferably as closer to 90° as possible.

After the resist 43 was removed, leads 47 were formed on thehigh-resistance amorphous layer 46. Note that the leads 47 can also beformed before the removal of the resist 43. As shown in FIG. 25C, theabove procedure makes it possible to manufacture a spin valve structuresensitive to the interface state without causing any deterioration incharacteristics.

As in the above structure, a high-coercive-force film can be usedwithout using any exchange bias layer consisting of FeMn or the like asa magnetization locking film. The material of the high-coercive-forcefilm is preferably one that can achieve a proper in-plane magneticanisotropy without using any undercoating film. In this example,therefore, the CoPtCr film which satisfies this characteristic was usedas the high-coercive-force film.

EXAMPLE 14

As shown in FIG. 26, a high-resistance amorphous layer 31, aferromagnetic film 32, an interlayer 33, another ferromagnetic film 32,and another high-resistance amorphous layer 31 were stacked in sequenceon a support substrate 30, and leads 35 were 10 formed on the uppermosthigh-resistance amorphous layer 31, manufacturing a magnetoresistanceeffect element.

As in the structure shown in FIG. 26, the antiferromagneticmagnetization arrangement between the ferromagnetic films 32 can berealized by using a magnetic field generated by a sense current or aself-bias effect resulting from the effect of a demagnetizing fieldcaused by the shape, without using any exchange bias layer consisting ofFeMn as a magnetization locking film.

In this case, the magnetic field generated by a sense current is appliedsuch that the direction of the magnetic field above the ferromagneticfilm 32 is opposite to that below the ferromagnetic film 32 in thedirection (indicated by g in FIG. 26) of the film width. In addition, todecrease the demagnetizing field in the direction of the film width, thetwo ferromagnetic films 32 are coupled antiferromagnetically. As aresult, the two ferromagnetic films 32 can be coupledantiferromagnetically without using any exchange bias layer. Therefore,when a signal magnetic field Hs is applied in the longitudinal direction(indicated by f in FIG. 26) of the film, the magnetizations of the twoferromagnetic films 32 are rotated and arranged in the longitudinaldirection of the film, thereby obtaining a ferromagnetic coupling. Theresult is a large ΔR/R derived from spin-dependent scattering.

EXAMPLE 15

As shown in FIG. 27, a CoCr alloy film as a high-resistanceferromagnetic film 161 was formed to have a film thickness of 1 nm on athermal oxide Si substrate 160 by using an ion beam sputtering process.Subsequently, on this high-resistance ferromagnetic film 161, a 3-nmthick CoFe alloy film as a first ferromagnetic film 162, a 2-nm thick Cufilm as a nonmagnetic film 163, and a 3-nm thick CoFe alloy film as asecond ferromagnetic film 164 were formed in sequence, forming a spinvalve type stacked film.

Thereafter, an FeMn film with a thickness of 15 nm was formed as anantiferromagnetic film 165 on the above stacked film. A protective film166 was formed on the antiferromagnetic film 165 as needed, andelectrodes 167a and 167b (spacing 10 μm) were formed, therebymanufacturing a spin valve type magnetoresistance effect element 168.

The resistance change rate of the spin valve type magnetoresistanceeffect element thus manufactured was found to have a high value of 14%at room temperature.

As a comparison, a spin valve type magnetoresistance effect element wasmanufactured following the same procedures as in Example 15 except thatno high-resistance ferromagnetic film 161 was formed. When thecharacteristics of this spin valve type magnetoresistance effect elementwere evaluated following the same procedures as in Example 15, theresistance change rate was found to be 12% at room temperature.

EXAMPLE 16

A Co₉₀ Fe₁₀ alloy film as a first ferromagnetic film, a Cu film as anonmagnetic film, a Co₉₀ Fe₁₀ alloy film as a second ferromagnetic film,and an FeMn film as an antiferromagnetic film were formed in this orderon a sapphire substrate. The resistance change rate (Δρ/ρ0) was measuredwhile changing the thickness (d_(FeCo)) of the first and secondferromagnetic films. The result is shown in FIG. 28. Note that thethicknesses of the first and second ferromagnetic films were the same,the thickness of the Cu film was 2.2 nm, and the thickness of the FeMnfilm was 15 nm. In this magnetoresistance effect element, electrodeswere formed on the antiferromagnetic film via a protective filmconsisting of, e.g., Ta, Ni, or NiCr with a high corrosion resistance ifnecessary. As is apparent from FIG. 28, the MR effect was enhanced whenthe d_(FeCo) was 5 nm or less. In addition, the peak appeared neard_(FeCo) =3 nm, and a preferable range was 2 to 4 nm.

As the thickness of the sandwich structure of ferromagneticfilm/nonmagnetic film (thin metal film)/ferromagnetic film decreases,electron scattering in the interface not in contact with the thin metalincreases, and the size effect of resistance appears. Assuming that thetotal film thickness of the sandwich structure is t and the mean freepath is 1₀, the variation (Δρ) of the specific resistance of thesandwich structure is proportional to 1₀ /t. As can be seen from FIG.28, when the Co-based ferromagnetic layer is used, the thickness of theferromagnetic layer is preferably 5 nm or less in order to obtain a goodMR effect although it changes depending on various conditions.

That is, if a low-resistance material with a specific resistance of,e.g., 30 μΩ·cm or less is in contact with the surface of theferromagnetic film not in contact with the thin metal film, electronspass through this interface to flow into the material with a specificresistance of 30 μΩ·cm or less, and this makes occurrence of effectivesurface scattering difficult. Therefore, to cause effective surfacescattering to make use of the size effect, it is effective to use amaterial with a specific resistance of 30 μΩ·cm or more or to decreasethe film thickness of the contacting material to 5 nm or less.

To take advantage of the size effect to thereby obtain a large MReffect, it is preferable that the film thickness of the Co-basedferromagnetic film be 5 nm or less. In this case, it is desirable to usea metal with a low specific resistance, such as Cu, Ag, or Au, as thethin intermediate metal film, and the film thickness of the thinintermediate metal film is preferably less than 5 nm in order to use thesize effect. If the film thicknesses of the two ferromagnetic films arelargely different from each other, the effect of the surface scatteringis also different between the two ferromagnetic films, and thisdecreases the rate of change in magnetic resistance. For this reason,the thickness ratio of the two ferromagnetic films is desirably between1:1 and 1:2.

EXAMPLE 17

As shown in FIG. 29, a CuPd alloy film as a nonmagnetic film 161 wasformed to have a thickness of 2 nm on a sapphire substrate 160 by an RFsputtering process. Subsequently, on this nonmagnetic film 161, a 1-nmthick CoFe alloy film as a first ferromagnetic film 162, a 2-nm thick Cufilm as a nonmagnetic film 163, and a 3-nm thick CoFe alloy film as asecond ferromagnetic film 164 were formed in sequence, thereby forming aspin valve type stacked film.

On this stacked film, an FeMn film with a thickness of 15 nm was formedas an antiferromagnetic film 165. On the antiferromagnetic film 165, aprotective film 166 was formed as needed, and electrodes 167a and 167bwere formed, thereby manufacturing a spin valve type magnetoresistanceeffect element 171.

In this magnetoresistance effect element, since unidirectionalanisotropy is imparted to the second ferromagnetic film 164 by theantiferromagnetic film 165, the magnetization is locked in one directionin a low magnetic field. In contrast, the first ferromagnetic film 162has its magnetization in the direction of a magnetic field even in a lowmagnetic field. Therefore, the angle defined between the magnetizationsof the two ferromagnetic fields can be controlled freely by changing theexternal magnetization. Note that the thickness of the antiferromagneticfilm 165 is preferably about 1 to 50 nm in order to impart an effectiveunidirectional anisotropy to the second ferromagnetic film 164.

The resistance change rate of the spin valve type magnetoresistanceeffect element 171 thus manufactured was measured. Consequently, theresistance change rate exhibited a high value of 8% at room temperaturealthough the thickness of the first ferromagnetic film 162 was as smallas 1 nm. In addition, when the above spin valve type magnetoresistanceeffect element 171 was used in reproduction of high-density magneticrecording in the form of a slender strip having a width of 2 μm and alength of 80 μm, with Cu leads spaced apart by a distance of 2 μm, itwas possible to remove Barkhausen noise.

For comparison, a spin valve type magnetoresistance effect element wasmanufactured following the same procedures as in Example 17 except thatno nonmagnetic film 161 was formed. When the characteristics of thisspin valve magnetoresistance effect element were evaluated in the samemanner as in Example 17, the resistance change rate showed only a smallvalue of 3% at room temperature.

In addition, another spin valve type magnetoresistance effect elementwas manufactured following the same procedures as in Example 17 exceptthat the film thickness of the first ferromagnetic film 162 was changedto 5 nm. When the characteristics of this spin valve typemagnetoresistance effect element were evaluated in the same manner as inExample 17, a resistance change rate of 6% could be obtained at roomtemperature. However, Barkhausen noise caused by a demagnetizing fieldwas observed. Furthermore, the Cu-CoFe interface need not be flat.

EXAMPLE 18

As shown in FIG. 30, a GaAs film doped with Te so as to obtain a carrierdensity of 10²⁰ cm⁻³ was formed to have a thickness of 10 nm as a thinfilm 172 with a long mean free path on a thermal oxide Si substrate 160by using an MBE process. Subsequently, on this Te-doped GaAs film 172, a1-nm thick CoFe alloy film as a first ferromagnetic film 162, a 2-nmthick Cu film as a nonmagnetic film 163, and a 4-nm thick CoFe alloyfilm as a second ferromagnetic film 164 were formed in sequence, therebyforming a spin valve type stacked film.

Thereafter, a 15-nm thick FeMn film as an antiferromagnetic film 165 wasformed on the above stacked film. A protective film 166 was formed onthe antiferromagnetic film 165 as needed, and electrodes 167a and 167bwere also formed, thereby manufacturing a spin valve typemagnetoresistance effect element 173.

The resistance change rate of this spin valve type magnetoresistanceeffect element was found to have a high value of 18% at roomtemperature. In addition, the above spin valve type magnetoresistanceeffect element was used in reproduction of high-density magneticrecording to measure an output signal voltage with a sense currenthaving a current density of 10⁵ A/cm². Consequently, it was possible toobtain a good value of 1 mV_(p-p).

As a comparison, a spin valve type magnetoresistance effect element wasmanufactured following the same procedures as in Example 18 except thatno Te-doped GaAs film 172 was formed. When the characteristics of thisspin valve type magnetoresistance effect element were evaluated in thesame manner as in Example 17, the resistance change rate presented onlya small value of 2% at room temperature.

EXAMPLE 19

A 10-nm thick Cu film was formed as an undercoating film on a glasssubstrate, and a Co₉₀ Fe₁₀ film was formed on the Cu film. These Cu andCo₉₀ Fe₁₀ films were formed by an RF double-pole sputtering process.Note that the sputtering was performed under the following sputteringconditions by applying a unidirectional magnetic field of about 4,000A/m to the vicinity of the substrate by using a permanent magnet duringthe film formation,

    ______________________________________                                        Preevacuation       1 × 10.sup.-4 Pa or less                            Ar sputter gas pressure                                                                           0.4 Pa                                                    RF supply power     CoFe: 300-500 W                                                               Cu: 160 W                                                 Sputtering rate     CoFe: 0.5-1 nm/s                                                              Cu: 1 nm/s                                                ______________________________________                                    

FIG. 31 shows the relationship between the Hc (in the axis of hardmagnetization) and the film thickness of the Co₉₀ Fe₁₀ film thus formed.FIG. 31 also shows the result obtained by forming a Co₉₀ Fe₁₀ filmdirectly on a glass substrate without forming any Cu undercoating filmas a comparative example. The coercive force Hc was measured by avibrating magnetometer.

As is apparent from FIG. 31, the normal Co₉₀ Fe₁₀ film having no Cuundercoating film exhibited a high Hc value of 2,000 A/m or more for afilm thickness of 20 nm or less. When a Cu undercoating film was formed,on the other hand, although a decrease in Hc was slight in the Co₉₀ Fe₁₀film with a film thickness of 20 nm, the Hc decreased largely to 400 to900 A/m when the film thickness was 10 nm or less. This demonstratesthat a Cu undercoating film formed between a glass substrate and a Co₉₀Fe₁₀ film can decrease the Hc of the Co₉₀ Fe₁₀ film. This Hc decreasingeffect was found if the film thickness of the Cu undercoating film wasone atomic layer or more. Since a sense current is shunted easily to Cuwith a low resistivity, the resistance change rate decreases if the filmthickness of the Cu undercoating film is increased. To prevent thisdecrease in the resistance change rate, the film thickness of the Cuundercoating film is preferably 2 nm or less.

Note that no decrease in Hc was found when a Co film was formed on aglass substrate via a Cu undercoating film. This indicates that theeffect of improving soft magnetism using an undercoating film isachieved when a ferromagnetic film consists of an alloy obtained byadding Fe to Co. It was found that a low Hc was realized especially whenthe concentration of Fe to be added to Co was 5% to 40%. This is sobecause if the Fe concentration is less than 5%, the hcp phase is mixed,and, if the Fe concentration exceeds 40%, the bcc phase is mixed easily.Examples of elements to be added to CoFe are Pd, Al, Cu, Ta, In, B, Zr,Nb, Hf, Mo, Ni, W, Re, Ru, Ir, Rh, Ga, Au, and Ag. The Hc reducingeffect can be achieved similarly when these elements were added.

As the undercoating film other than the Cu film, it is possible to use afilm consisting of a material having the fcc phase and a larger latticeconstant than that of CeFe, e.g., a Cu-based alloy, Pd, Al, or amagnetic film having the fcc phase. It was found that the Hc reducingeffect could be obtained similarly by using these materials.

EXAMPLE 20

A Cu undercoating film with a thickness of 5 to 6 nm was formed on aglass substrate, and a Co₉₀ Fe₁₀ film, a 2-nm thick Cu interlayer, andanother Co₉₀ Fe₁₀ film were formed in sequence on the Cu undercoatingfilm. These films were formed under the same film formation conditionsas in Example 19.

FIG. 32 shows the relationship between the Hc (in the axis of hardmagnetization) and the film thickness of the Co₉₀ Fe₁₀ film in thisstacked film (Cu/CoFe/Cu/CoFe). Like in FIG. 31, the result obtained byforming a Co₉₀ Fe₁₀ film on a glass substrate without forming any Cuundercoating film is also shown in FIG. 32.

As shown in FIG. 32, in the stacked film having no Cu undercoating film,although the Hc increased abruptly when the film thickness of the unitCo₉₀ Fe₁₀ film was 5 nm or more, the Hc was 800 A/m for a film thicknessof 3 nm or less. That is, the Hc could be reduced simply by forming a Cuinterlayer. The Hc could be further reduced by providing a Cuundercoating film to this stacked film; i.e., a low Hc of 220 to 400 A/mcould be obtained when the film thickness of the unit Co₉₀ Fe₁₀ film was7 nm or less. Therefore, the Hc can be decreased to be much lower thanthat in Example 19 in the Co₉₀ Fe₁₀ stacked film using the Cuundercoating film and the Cu interlayer.

FIG. 33 shows the magnetization curves (in the axis of easymagnetization) of a stacked film with a structure of 5 nm Cu/2.2 nm Co₉₀Fe₁₀ /2 nm Cu/2.2 nm Co₉₀ Fe₁₀. As is apparent from FIG. 33, theresidual magnetization was 90% or more even when the magnetic field was0, indicating that the magnetizations of these two Co₉₀ Fe₁₀ferromagnetic films show a ferromagnetic behavior rather than anantiferromagnetic behavior.

EXAMPLE 21

A (CoFe/Cu)_(n) film was formed under the same film formation conditionsas in Example 19 by setting a unit film thickness of a Co₉₀ Fe₁₀ film to1.5 nm and a unit film thickness of a Cu film to 1.5 nm, and therelationship between the Hc and the stacking number n was checked. Theresults are shown in FIG. 34. The relationship was examined for astacked film in which Co₉₀ Fe₁₀ films and Cu films were stacked in thisorder on a glass substrate and a stacked film in which Cu films and Co₉₀Fe₁₀ films were stacked in this order on a glass substrate (in thiscase, the first Cu film is regarded as an undercoating film).

As shown in FIG. 34, when the Co₉₀ Fe₁₀ film was formed first for astacking number of 2, the Hc took a slightly high value of 650 A/m.However, when the stacking number was 4 to 8, the Hc presented a lowvalue of 100 to 300 A/m regardless of whether the Co₉₀ Fe₁₀ film or theCu film was formed first. The reason for this is assumed that the effectof the Cu undercoating film is weakened as the stacking numberincreases, and this decreases the Hc regardless of the presence/absenceof the Cu undercoating film (the first Cu film). Note that themagnetization curve in this case also had a shape indicatingferromagnetic coupling as in FIG. 33.

It was also found from section transmission electron microscopicobservation or measurements of diffraction peak half-widths of X-raydiffraction curves that in this stacked film, the crystal grain size waslarge, i.e., the crystal grew continuously and epitaxially in theinterface between the Cu film and the Co₉₀ Fe₁₀ film. Therefore, unlikea conventional multilayered film such as Fe/C which achieves softmagnetism by a fine crystal effect using a crystal growth preventingeffect in the interface between a nonmagnetic film and a ferromagneticfilm, the stacked film of this example has no excessive increase inresistance and hence can be applied to a magnetoresistance effect filmusing spin-dependent scattering. Furthermore, the Cu-CoFe interface neednot be flat.

EXAMPLE 22

It is known that in a (Co₉₀ Fe₁₀ /Cu)_(n) film, the magnetizations offerromagnetic films adjacent to a Cu film are coupledantiferromagnetically or ferromagnetically in accordance with the filmthickness of the Cu film. FIG. 35 shows the relationship between the Hs(saturation magnetic field) in the axis of hard magnetization and thefilm thickness of a unit Cu film in (Co₉₀ Fe₁₀ (1 nm)/Cu)₁₆. When thefilm thickness of the Cu film was set near 1 nm or 2 nm, a large Hs (12to 240 kA/m) caused by the antiferromagnetic coupling betweenneighboring ferromagnetic films resulted. In this case, the stacked filmalso presented a magnetization curve indicating antiferromagneticcoupling in which residual magnetization decreased largely as shown inFIG. 36 even in the axis of easy magnetization. With other filmthicknesses, on the other hand, the stacked film exhibited an Hs (1,000to 2,000 A/m) corresponding to induced magnetic anisotropy of Co₉₀ Fe₁₀like in the magnetization curves shown in FIG. 33. In addition, theresidual magnetization of the magnetization curve in the axis of easymagnetization was 90% or more, demonstrating characteristics withantiferromagnetic coupling.

It is clear from FIG. 35 that ferromagnetic coupling can be obtained bysetting the film thickness at an intermediate value of about 1.5 nm.Since ferromagnetic coupling has a low Hs, it is possible to increasethe permeability in the axis of hard magnetization which is important inapplying the structure to a magnetic sensor, such as a magnetic head. Inthis example, therefore, the film thickness of the Cu film is preferablyan intermediate value by which no antiferromagnetic coupling is caused,unlike in the case of a conventional artificial lattice film whichexhibits an enormous magnetoresistance effect.

EXAMPLE 23

Following the same procedures as in Example 19, a ferromagnetic stackedfilm unit 51 was formed on a substrate 50. This ferromagnetic stackedfilm unit 51 is a stacked film of a Cu film as a nonmagnetic film and aCo₉₀ Fe₁₀ film as a ferromagnetic film shown in Examples 21 and 22.Subsequently, a nonmagnetic film 52 with a thickness different from thatof the nonmagnetic film of the ferromagnetic stacked film unit 51 wasformed on the ferromagnetic stacked film unit, and another ferromagneticstacked film unit 51 was formed on the nonmagnetic film 52. Anantiferromagnetic film 53 consisting of, e.g., FeMn, NiO, or NiCoO wasformed on the resultant structure, and a protective film 54 was formedon the antiferromagnetic film 53. This protective film 54 is formed asneeded. Lastly, electrode terminals 55 were formed on the protectivefilm 54 to supply a current to edge portions, thereby completing amagnetoresistance effect element shown in FIG. 37.

In this structure, an exchange bias can be applied to the ferromagneticstacked film unit 51 in direct contact with the antiferromagnetic film53 by performing formation of the ferromagnetic stacked film unit 51 andthe antiferromagnetic film 53 in a unidirectional magnetic field. Notethat a CoFe single-layered film with soft magnetism slightly lower thanthat of the ferromagnetic stacked film unit 51 is also usable instead ofthe ferromagnetic stacked film unit 51, since the magnetization of theferromagnetic film of the ferromagnetic stacked film unit 51 which isexchange-coupled to the antiferromagnetic film 53 is locked. Note alsothat the interface of the ferromagnetically-coupled CoFe/Cu need not beflat; that is, an identical effect can be achieved even if the interfaceis disturbed significantly as shown in FIG. 38.

FIGS. 39 and 40 show the magnetization curves and the resistance changecharacteristics (in the direction of the axis of easy magnetization),respectively, of a magnetoresistance effect element manufactured byforming a (1 nm Co₉₀ Fe₁₀ /1.2 nm Cu)₄ film as the ferromagnetic stackedfilm unit 51, a 2.5-nm thick Cu film as the nonmagnetic film 52, a 10-nmthick FeMn film as the antiferromagnetic film 53, and a 6-nm thick Cufilm as the protective film 54. The resistance was measured by use of afour-terminal method.

As is apparent from FIGS. 39 and 40, magnetizations between the twoferromagnetic stacked film units 51 were coupled antiferromagneticallyfor H>800 A/m, and coupled ferromagnetically for H<500 A/m. That is, themagnetizations changed from the ferromagnetic coupled state to theantiferromagnetic coupled state for H=500 to 800 A/m. The resistancechanged largely with this slight magnetic field of H=500 to 800 A/m,i.e., with this slight hysteresis, and the resistance change rate ΔR/Rat this time was 8%.

For comparison, FIGS. 41 and 42 show the magnetic curves and theresistance change characteristics, respectively, of a magnetoresistanceeffect element with a spin valve structure shown in FIG. 37 whichconsisted of Co₉₀ Fe₁₀ single-layered films (in which each ferromagneticstacked film unit 51 was replaced with a Co₉₀ Fe₁₀ single-layered film).

As shown in FIGS. 41 and 42, the hysteresis of the magnetic curves waslarge compared to the resistance change shown in FIG. 40, and as aresult a large hysteresis also existed in the resistance changecharacteristics. The ΔR/R was about 6.5%, which was smaller than theresistance change shown in FIG. 39.

From the above description, it is obvious that the magnetoresistanceeffect element with the spin valve structure using the ferromagneticstacked film of the present invention has a good soft magnetism andshows a large resistance change with a slight magnetic field. Inaddition, the resistance change rate is high because the Co₉₀ Fe₁₀ /Cuinterface is present inside the ferromagnetic stacked film unit.

The examples of the (CoFe/Cu)_(n) stacked film have been described indetail above. This spin valve structure, however, can achieve the sameeffect even by using a stacked film constituted by a differentferromagnetic film (e.g., NiFe, NiFeCo, or Co) and a differentnonmagnetic film (e.g., a Cu-based alloy). Table 4 below shows theresistance change rate in the axis of easy magnetization and the Hc ofthe spin valve structure shown in FIG. 37 when the ferromagnetic stackedfilm unit 51 was replaced with several different ferromagneticallycoupled multilayered films.

                  TABLE 4                                                         ______________________________________                                                                    Resistance                                        Feeromagnetic stacked       change                                            film unit         Hc (A/m)  rate (%)                                          ______________________________________                                        Co.sub.20 Fe.sub.15 Ni.sub.65 1 nm thick/                                                        80       6.9                                               Cu 0.7 nm thick)4                                                             Co.sub.90 Fe.sub.10 1 nm thick/                                                                 660       7.9                                               Cu.sub.80 Ni.sub.20 0.7 nm thick)4                                            Co.sub.80 Fe.sub.20 1 nm thick/                                                                 320       6.3                                               Cu 0.7 nm thick)4                                                             ______________________________________                                    

Table 4 reveals that even when the ferromagnetic multilayered films withcombinations other than CoFe/Cu are used, the Hc can be decreasedcompared to the spin valve film (see Table 1) using the single-layeredmagnetic film, and a resistance change rate equal to or higher than thatof the spin valve film using the single-layered magnetic film can berealized.

EXAMPLE 24

A magnetoresistance effect element was manufactured by using, in thestructure shown in FIG. 37, a 4-nm thick Cu undercoating film and 5-nmthick Co₉₀ Fe₁₀ as the ferromagnetic stacked film unit 51 in contactwith the substrate, and an 8-nm thick Co₉₀ Fe₁₀ single-layered film asthe ferromagnetic stacked film unit 51 in contact with theantiferromagnetic film 53. FIGS. 43A and 43B show the magnetizationcurves of the resultant magnetoresistance effect element, and FIG. 54shows the resistance change characteristics of the element.

As shown in FIG. 43A, the Hc exhibited a relatively large value of 800A/m or less in the axis of easy magnetization, but, as shown in FIG.43B, presented a low value of 100 A/m or less in the axis of hardmagnetization. In addition, as can be seen from FIG. 44, the resistancechange rate ΔR/R was 7.2% in the axis of easy magnetization and 2.8% inthe axis of hard magnetization. It is assumed that the resistance changerate was low in the axis of hard magnetization because an antiparallelmagnetization arrangement was insufficient due to ferromagnetic couplingbetween the two ferromagnetic films. Therefore, the ΔR/R equivalent tothat in the axis of easy magnetization can be obtained by applying abias magnetic field for promoting the antiparallel magnetizationarrangement by using a hard magnetic film or the like. That is, it ispossible to obtain both a good soft magnetism and a high ΔR/R even bythe use of the stacked film constituted by the Cu undercoating film andthe Co₉₀ Fe₁₀ film.

EXAMPLE 25

The ferromagnetic stacked film units 51 used in Example 23 andnonmagnetic films 52 each having a different thickness from that of thenonmagnetic film contained in the ferromagnetic stacked film unit 51were stacked alternately at least twice on a substrate 50. In addition,a protective film 54 was formed on the uppermost nonmagnetic film 52.This protective film 54 is formed if necessary. Lastly, electrodeterminals 55 for supplying a current to edge portions were formed,thereby manufacturing a magnetoresistance effect element shown in FIG.45.

FIGS. 46 and 47 show the magnetization curves in the axis of hardmagnetization and the resistance change characteristics of the abovemagnetoresistance effect element manufactured by stacking (1 nm Co₉₀Fe₁₀ /0.6 nm Cu)₄ films as the ferromagnetic stacked film units 51 and2.2-nm thick Cu films as the nonmagnetic films 52 eight times (i.e.,stacking number n=8).

As shown in FIGS. 46 and 47, the saturation magnetic film Hs showed arelatively small value of 6,000 A/m, and the Hc also had a small valueof 240 A/m. At this time, the resistance change rate was 12% or less, amagnetic field by which the resistance change was saturated almostcoincided with the saturation magnetic field Hs on the magnetizationcurves, and a hysteresis almost agreed with the Hc on the magnetizationcurves. This indicates that a high resistance change rate was obtainedby a slight magnetic field.

EXAMPLE 26

A (1 nm Co₉₀ Fe₁₀ /1.1 nm Cu)₁₆ stacked film 61 was formed on the (110)plane of an MgO substrate 60 whose surface was processed into a mirrorsurface. The stacked film 61 was then patterned into stripes of 1×8 mm²through a metal mask. Subsequently, electrode terminals 62 for supplyinga current to edge portions were formed on the stacked film 61,manufacturing a magnetoresistance effect element. Note that a 5.5-nmthick Cu film may be formed as a protective film on the stacked film 61.Note also that Co₉₀ Fe₁₀ was used as the composition of the CoFe-basedalloy film in respects of a high resistance change rate [Japan AppliedMagnetics Society Journal, 16, 313 (1992)] and good soft magneticcharacteristics.

In this structure, the Co₉₀ Fe₁₀ film was formed first on the (110)plane of the MgO substrate 60, since it is not possible to obtain alarge resistance of 10% or more if the Cu film is formed first.Referring to FIG. 48, wavy lines shown in the stacked film 61 indicatethe section of a principal growth plane. An MR sense current (Is) isflowed in this direction in which the principal growth plane fluctuates.

As a film formation apparatus for forming the stacked film 61, amulti-element simultaneous sputtering apparatus was used. Thissputtering apparatus is so designed as to be able to perform RF sputterfor a Co₉₀ Fe₁₀ target and DC sputter for a Cu target, forming films bypassing a substrate applied with a DC bias above the individual targetsalternately. A cryopump was used as a main exhaust pump. After a vacuumchamber was evacuated to 5×10⁻⁷ Torr or less, the above film formationapparatus was used to introduce Ar gas into the vacuum chamber,performing sputtering at about 3 mTorr.

The resistance change rate and the crystal structure of the resultantmagnetoresistance effect element were examined. As the resistance changerate, a resistance change in the direction of a static magnetic fieldwas measured by a four-terminal method. In this measurement, the currentdensity was set at 2.0 to 2.5 kA/cm². The crystal structure wasevaluated by performing 74 -2θ scan and measuring a rocking curverelated to a principal diffraction plane by using x-ray diffractionunder the following measurement conditions. X-ray DiffractionMeasurement Conditions

(1) θ-2θ scan

Cu-Kα, 40 kv, 200 mA

Scan width: 2θ=2° to 100°

Step width: 0.03°

Coefficient time: 0.5 sec

(2) Rocking curve

Cu-Kα, 40 kV, 200 mA

Scan width: 2θ=20° to 60°

Step width: 0.04°

Coefficient time: 0.5 sec

FIGS. 49A and 49B illustrate the x-ray diffraction curves of the stackedfilm of the magnetoresistance effect element measured by the θ-2θ scan.As shown in FIG. 49B, a high diffraction peak corresponding to fcc-phase(220)) plane reflection was found near 2θ=75°. This X-ray diffractioncurve therefore indicates that the principal growth plane of the stackedfilm was the fcc-phase (220)) plane having strain in one direction. Notethat a peak near 2θ=4° shown in FIG. 49A corresponds to diffractioncaused by a stacking period (about 2.1 nm)

Subsequently, rocking curves were measured for this principal growthplane in the directions of the [100] axis and the [110] axis. Theresults are shown in FIGS. 50A and 50B. FIG. 51A shows the rocking curvemeasured along the [110] axis, in which one peak is present near θ=38°.FIG. 50B, on the other hand, shows the rocking curve in the direction ofthe [100] axis, in which two peaks appear near θ=33° and 41°.

FIGS. 51A and 51B are views showing a film structure estimated from therocking curves shown in FIGS. 50A and 50B. Wavy layers illustrated inFIG. 51A indicate the fcc-phase (110) plane of the principle growthplane. Although an average crystal growth plane measured by the θ-2θscan X-ray diffraction process is (110), this (110) plane shown in FIG.51A fluctuates in the direction of the [100] axis. On the other hand, afluctuation along the [110] axis is very small. This result correspondsto the two peaks of the rocking curve (measured in the direction of the[100] axis) shown in FIG. 50B and the single peak of the rocking curve(measured in the direction of the [110] axis) shown in FIG. 50A.

FIG. 51B illustrate the in-plane component distribution of a normal tothis growth plane. This in-plane anisotropy is large along the [100]axis and small along the [110] axis because of the large fluctuation inthe direction of the [100] axis. As will be described later, theresistance change rate (ΔR/R) when an MR sense current was flowed in thedirection of the [110] axis was about 30%, whereas that obtained whenthe current was flowed along the [100] axis was about 35%.

The magnetic characteristics of this stacked film were measured. FIGS.52A and 52B show the magnetization curves based on the measurements.FIG. 52A illustrates the magnetization curves when an external magneticfield H was applied parallel to the [100] axis, and FIG. 52B illustratesthe magnetization curves when the external magnetic field H was appliedparallel to the [110] axis. Note that the magnetic characteristics ofthe magnetoresistance effect element were measured with a maximumapplied magnetic field of 1.2 MA/m by using a vibrating magnetometer(VSM). Note also that a magnetization quantity M of each magnetizationcurve is represented by a value obtained by normalizing a saturationmagnetization Ms.

As can be seen from FIGS. 52A and 52B, the [100] axis was the axis ofeasy magnetization, and the [110] axis was the axis of hardmagnetization. At this point, the saturation magnetic field of the axisof easy magnetization was about 240 kA/m, and that of the axis of hardmagnetization was about 960 kA/m.

As described above, this example provides a magnetoresistance effectelement comprising a stacked film formed by sequentially stacking aferromagnetic film and a nonmagnetic film at least once on a substrate,wherein the direction of a sense current is set along the direction offluctuation of the crystal orientation plane of the stacked film.

In this example, a normal to the principal crystal orientation plane ofthe stacked film has a component in the film plane due to thefluctuation of the crystal orientation plane, and this component in thefilm plane has anisotropy. Alternatively, a normal to a plane defectoccurring in the crystalline stacked film has a fluctuation into thefilm plane, and this fluctuation has anisotropy in the film plane. Adirection in which this anisotropy is strong is a direction along whichferromagnetic atoms and nonmagnetic atoms are likely to exist togetherin the atomic plane of film growth.

By flowing a sense current in this direction, i.e., the direction inwhich the anisotropy derived from the in-film plane component becomeslargest, a probability of electrons causing spin-dependent scattering israised. Consequently, the magnetoresistance effect element shows ahigher resistance change rate.

EXAMPLE 27

By changing the bias to be applied to a substrate, several differentmagnetoresistance effect elements each having the same stacked filmstructure as in Example 26 were manufactured, FIG. 53 shows the biasvoltage dependency of the resistance change rate. Note that themeasurements were performed by flowing a current parallel to the [100]axis and the [110] axis perpendicular to each other on the (110) planeof the MgO substrate.

As is apparent from FIG. 53, the bias dependency of the resistancechange rate was low in either axis, i.e., was about 35% in the [100]axis and about 30% in the [110] axis. That is, the resistance changerate in the [100] axis was higher than that in the [110] axis.

EXAMPLE 28

A magnetoresistance effect element was manufactured following the sameprocedures as in Example 26 except that a (2 nm Cu/1 nm Co₉₀ Fe₁₀)₁₆film was used as a stacked film.

when the film thickness of the Cu film was increased to 2 nm asdescribed above, the resistance change rate was approximately 25% when acurrent was flowed in the direction of the [100] axis, and approximately19% when the current was flowed in the direction of the [110] axis. Thisindicates that the direction dependency of the resistance change ratewas held even when the film thickness of the Cu film was increased. Alsoin this case, two peaks were found in the [100] axis as shown in FIG.50B and one peak was found in the [110] axis as shown in FIG. 50A on therocking curves of the principal growth plane (the fcc-phase (220))plane).

Even when the film thicknesses of the Cu film and the Co₉₀ Fe₁₀ filmwere changed to 0.3 nm to 10 nm, respectively, in the above arrangement,the above tendency of the rocking curve remained unchanged, i.e., thefluctuation was larger in the [100] axis. The resistance change rate wasalso higher in the [100] axis.

In addition, even when the stacking number was changed from 2 to 70 inthe above arrangement, the tendencies of both the rocking curve and theresistance change rate still remained the same; that is, a largerresistance change was obtained when a sense current was flowed in thedirection of the [100] axis.

EXAMPLE 29

A magnetoresistance effect element was manufactured following the sameprocedures as in Example 26 except that a (1 nm Ru/1 nm Co₉₀ Fe₁₀)₁₆film was used as a stacked film.

The ΔR/R of this magnetoresistance effect element was larger when asense current was flowed in the direction of the [100] axis than whenthe sense current was flowed in the direction of the [110] axis. Thistendency remained unchanged even when the film thickness of the Ru filmwas changed.

The above phenomenon was also found when a Co film was used in place ofthe Co₉₀ Fe₁₀ film. Even when Ag, Au, Pd, Pt, and Ir were used in placeof Ru as the material of the stacked film, it was possible to confirmthe difference in the ΔR/R between different axial directions on the(110) plane of the MgO substrate.

EXAMPLE 30

A magnetoresistance effect element was manufactured following the sameprocedures as in Example 26 except that a (1.1 nm Cu/1.5 nm Ni₈₀ Fe₂₀)₁₆film was used as a stacked film.

When a sense current was flowed in the direction of the [100] axis ofthe stacked film of this magnetoresistance effect element, the resultingresistance change rate was 21%. When, on the other hand, the sensecurrent was flowed along the [110] axis, the resistance change rate was17%. In this stacked film, the crystal growth plane was the fcc-phase(110) plane, as in the Co₉₀ Fe₁₀ /Cu stacked film, and it was confirmedfrom rocking curve measurement that the growth plane fluctuated in thedirection of the [100] axis. Even when the film thicknesses of the Ni₈₀Fe₂₀ film and the Cu film were changed from 0.5 nm to 50 nm, the abovetendency remained the same.

It was also found that even if Co, a CoFe alloy, an NiFe alloy, Fe, andan FeCr alloy were used as the material of the ferromagnetic film andCu, Au, Ag, Cr, Ru, and a CuNi alloy were used as the material of thenonmagnetic film, high resistance change rates were obtained providedthat the direction of the crystal axis in which the principal growthplane of the stacked film fluctuated was parallel to the direction ofthe sense current.

EXAMPLE 31

A 1.5-nm thick Co film, a 50-nm thick Ge film, and a 1.5-nm thick Aufilm were formed on the (110) plane of a GaAs substrate. A (0.9 nm Cu/1nm Co₉₀ Fe₁₀)₂₀ film shown in FIG. 54 was also formed on the resultantstructure by using an MBE process. Referring to FIG. 54, referencenumeral 70 denotes the Cu film; and 71, the Co₉₀ Fe₁₀ film. In addition,a 5-nm thick Ge film was formed as a protective film on the stackedfilm, thereby manufacturing a magnetoresistance effect element. Thisstacked film showed fcc-phase (111) plane growth. The resistance changerate was approximately 15% regardless of the direction of a sensecurrent.

Separately, another magnetoresistance effect element was manufacturedfollowing the same procedures as described above except that thethickness of the Au undercoating film was changed to 0.8 nm.

The two magnetoresistance effect elements were observed by using atransmission electron microscope. Consequently, the element with the1.5-nm thick Au undercoating film showed almost no lattice defect andhad an excellent crystallinity. On the other hand, in the element withthe 0.8-nm thick Au undercoating film, although (111) plane orientationwas presented, the (100) plane slipped in the direction of the <110>axis, and the consequent stacking defect was observed. The resistancechange rate of this magnetoresistance effect element was measured in the<211> axis and the <110> axis. As a result, the resistance change ratewhich was about 15% in the <110> direction was increased to 17% in the<211> direction. This indicates that a defect having directivity givesrise to the sense current direction dependency of the resistance changerate.

FIG. 55 shows an atomic arrangement in the stacked film shown in FIG.54. Referring to FIG. 55, since the (100) atomic plane slips in the<110> direction, the number of interfaces encountered per unit lengthwhen a current flows in the <211> direction is different from that whena current flows in the <110> direction; the number is larger in the<211> direction. It was found that this crystal axial directiondependency of the number of spin-dependent scattering sites ofconduction electrons produced by such a lattice defect with directivityresulted not only from the stacking defect described above but from atwinned crystal defect. An example of the twinned crystal detect will bedescribed below.

A3-nm thick Au undercoating film was formed on the (100) plane of a GaAssubstrate, and a (1 nm Co₉₀ Fe₁₀ /1.1 nm Cu)₁₆ stacked film was formedon it. This stacked film showed fcc-phase (100) plane orientation. Atthis point, a twinned crystal was produced around the <111> axis. FIG.56 shows an atomic arrangement when the section of the stacked film wasobserved in the <110> direction. As shown in FIG. 56, when the twinnedcrystal was produced around the <111> axis, an interface between Cuatoms and Co or Fe atoms appeared in the <110> direction.

The sense current direction dependency of the resistance change rate ofthis stacked film was measured along the <110> axis and the <100> axis.FIG. 57 illustrates the twinning plane of the stacked film grown on the(100) plane and the correlation between the current direction and theresistance change rate. As can be seen from FIG. 57, the resistancechange rate was 18% when a sense current was flowed in the direction ofthe <110> axis and 16% when the sense current was flowed along the <100>axis. That is, the resistance change rate was higher along the <110>axis which met the (111) plane with a larger angle. When no twinnedcrystal was formed, on the other hand, the resistance change rate wasfound to have no sense current direction dependency.

EXAMPLE 32

A (1.1 nm Cu/1 nm Co₉₀ Fe₁₀)₁₆ artificial lattice film was formed on aglass substrate while applying a DC bias to the substrate. Theresistance change rate was measured by changing the magnitude of thebias to be applied to the substrate. FIG. 58 shows the dependency (biasdependency) that the resistance change rate had on the DC bias to beapplied to the substrate.

As can be seen from FIG. 58, the resistance change rate increased as theDC bias was raised and presented a peak value of about 28% when the biaswas -50 V. when the bias was further increased, the resistance changerate decreased.

The crystallinities of several different artificial lattice filmsmanufactured by changing the DC bias were evaluated. Consequently, theprincipal growth plane was the fcc-phase (111) plane in all of theartificial lattice films. FIG. 59 illustrates the bias dependency of thelong periodic structure reflection peak which resulted from a stackingperiod (2.1 nm) and appeared near 2θ=4°. FIG. 60 illustrates the biasdependency of the peak intensity of the principal growth plane which wasreflected by the fcc-phase (111) plane and appeared near 2θ=44°.

As shown in FIG. 59, the long periodic structure reflection intensityhad a slight peak when the bias was about -20 V, but it cannot be saidthat this reflection intensity has a strong correlation with the bias.In addition, as shown in FIG. 60, although the fcc-phase (111) planereflection intensity also had a slight peak when the bias was around -10V, it cannot be said that this reflection intensity has a strongcorrelation with the bias.

When the Co₉₀ Fe₁₀ film was used as the ferromagnetic film, bulkspin-dependent scattering increased, so the interface structure was nolonger sensitive compared to that when the Co film was used as theferromagnetic film. Note that it is reported that the resistance changerate depended largely on the film structure when the Co film was used asthe ferromagnetic film.

FIG. 61 shows the bias dependency of a coercive force (Hc). As isapparent from FIG. 61, although good soft magnetic characteristics of200 A/m or less were obtained when the bias was at most about -50 V, thecoercive force began to increase when the bias reached about -60 V.Therefore, optimal conditions for the resistance change rate and thecoercive force can be selected by selecting the magnitude of the Dc biasto be applied. Note that it was also possible to select optimal pointsfor the resistance change rate and the coercive force even when an Sisubstrate, a ceramic substrate, a GaAs substrate, and a Ge substratewere used in place of the glass substrate.

EXAMPLE 33

An example of the present invention for detecting a signal magneticfield by using rotations of magnetizations of two ferromagnetic filmshaving a spin-dependent scattering ability will be described first.

As shown in FIG. 62, an undercoating film 81 for controlling orientationof an antiferromagnetic film, an antiferromagnetic film 82, aferromagnetic film 83 having a spin-dependent scattering ability, anonmagnetic film 84, a ferromagnetic film 85, and anotherantiferromagnetic film 82 were formed in sequence on a substrate 80.Subsequently, electrode terminals 86 were formed on the uppermostantiferromagnetic film 82. A protective film can also be formed on thisantiferromagnetic film 82 as needed. when the antiferromagnetic filmconsists of FeMn, it is desirable that the material of the undercoatingfilm 81 be Cu, a Cu alloy, such as Cuv or CuCr, a metal having anonmagnetic fcc phase, such as Pd, or a metal having a magnetic layer,such as NiFe or CoFeTa. Use of the magnetic layer makes it possible toobtain a good exchange bias even with a small film thickness (i.e., witha small shunt current). The antiferromagnetic film 82 consisted of,e.g., FeMn, NiO, or PtMn and had a film thickness of 5 to 50 nm. Theferromagnetic films 83 and 85 consisted of e.g, NiFe, Co, CoFe, orNiFeCo and had a film thickness of 0.5 to 20 nm. The nonmagnetic film 84was made of, e.g., Cu, Au, or Ag and had a film thickness of 0.5 to 10nm. The antiferromagnetic film 82 need not be formed on the entiresurface of the ferromagnetic film 85 but may be formed only on edgeportions (in the vicinities of the electrode terminals 86) on both thesides of the ferromagnetic film 83.

During the formation of at least the ferromagnetic film 83, aunidirectional static magnetic field is applied in the x direction(sense current direction) shown in FIG. 62. Consequently, anexchange-coupled bias magnetic field is applied to the ferromagneticfilm 83 in the direction of the static magnetic field. During theformation of at least the antiferromagnetic film 82, on the other hand,a static magnetic field is applied in a direction (-x direction)different by 180° from the direction of the magnetic field appliedduring the formation of the ferromagnetic film 83. Consequently, anexchange-coupled bias magnetic field is applied to the ferromagneticfilm 85 in a direction different by 180° from the direction of theexchange-coupled bias magnetic field applied to the ferromagnetic film83. The result is that the directions of magnetizations of the twoferromagnetic films 83 and 85 are antiparallel to each other when thesignal magnetic field is 0. Note that the signal magnetic field Hs isapplied in the y direction shown in FIG. 62.

The following method is also applicable as the method of applying thebias magnetic fields in the opposite directions to the ferromagneticfilms 83 and 85 by the use of the antiferromagnetic film 82. That is,films having different N eel temperatures are used as the twoantiferromagnetic films 82, and a static magnetic field heat treatmentis performed at a temperature higher than those N eel temperatures.While the temperature is lowered, the direction of the static magneticfield is reversed 180° at an intermediate temperature between the N eeltemperatures of the two antiferromagnetic films. As a result, biasmagnetic fields in opposite directions can be applied to theferromagnetic films 83 and 85.

unlike films with a conventional spin valve structure, this examplemakes use of the magnetization rotation of the ferromagnetic filmapplied with the exchange bias from the antiferromagnetic film.Therefore, it is desirable that this exchange bias magnetic field be amagnetic field which is not so strong but by which Barkhausen noise canbe suppressed. For example, the strength of the magnetic field is amaximum of 5 kA/m although it depends on the track width of a magnetichead or the like. In films with a current spin valve structure, however,the use of an exchange bias magnetic field generated by anantiferromagnetic film consisting of FeMn is common. In this case, anexchange bias of 10 kA/m or more is produced when this FeMn film and aferromagnetic film consisting of NiFe or the like are stacked directly.To reduce this exchange bias, there is a method by which a film foradjusting the exchange bias, such as a ferromagnetic film with a lowsaturation magnetization or a nonmagnetic film, is inserted between theantiferromagnetic film and the ferromagnetic film. Alternatively, asshown in FIG. 63, nonmagnetic films 87 and 88 may be interposed in theferromagnetic films 83 and 85, respectively. That is, the ferromagneticfilms 83 and 85 may be separated into films 83a and 83b, and films 85aand 85b, respectively.

In the method of interposing the nonmagnetic films into theferromagnetic films, a strong exchange bias is applied to theferromagnetic films 83a and 85a in contact with the antiferromagneticfilms, but a weak exchange bias is applied to the ferromagnetic films83b and 85b not in contact with the antiferromagnetic films. Themagnitude of the exchange bias applied to the ferromagnetic films 83band 85b not in contact with the antiferromagnetic films can be reducedin accordance with the type of a material or film thickness of thenonmagnetic films 87 and 88.

The angle defined between the magnetizations of the ferromagnetic films83a and 83b and the angle defined between the magnetizations of theferromagnetic films 85a and 85b change from a ferromagnetic angle to anantiferromagnetic angle upon magnetization rotation caused by the signalmagnetic field. In contrast, the angle defined between themagnetizations of the ferromagnetic films 83b and 85b in centralportions of the films changes from the antiferromagnetic angle to theferromagnetic angle. Therefore, spin-dependent scattering of the formerand that of the latter cancel each other out. It is therefore desirablethat the materials of the ferromagnetic films 83a and 85a and thenonmagnetic films 87 and 88 have no spin-dependent scattering abilityand high resistances. It is also desirable that the thickness of theferromagnetic films 83a and 85a in contact with the antiferromagneticfilms be smaller than that of the ferromagnetic films 83b and 85b not incontact with the antiferromagnetic films.

With the above arrangement, the magnetization directions of theferromagnetic films 83 and 85 can be arranged to be antiparallel to eachother when the magnetic field is 0. The outcomes are as follows. First,it is possible to realize a state in which the angle defined between themagnetizations of the two ferromagnetic films change from 0° to 180°through the magnetization rotation of these ferromagnetic films, even ifthe signal magnetic field is applied in the direction of the axis ofhard magnetization (the y direction in FIG. 63). Second, since the biasmagnetic field is applied to the two ferromagnetic fields, domain wallscan be eliminated from the two ferromagnetic films, and this suppressesBarkhausen noise. Third, in a system in which the sense current and thesignal magnetic field are perpendicular to each other, it is possible toobtain both a regular magnetoresistance effect that is significant whenan NiFe film or the like is used, and a resistance change resulting fromspin-dependent scattering, which cancel each other out in a conventionalspin valve structure. Therefore, an increase in ΔR/R can be expected.

EXAMPLE 34

In Example 33, the method by which the magnetization directions of twoferromagnetic films are set to be antiparallel to each other by the useof two antiferromagnetic films is explained. It is, however, notnecessary to apply a bias magnetic field by using only theantiferromagnetic films, but a leakage magnetic field from a hardmagnetic film or a demagnetizing field generated when a film isprocessed into a fine pattern is also usable. This example will bedescribed next.

As shown in FIG. 64, a ferromagnetic film 91 having a spin-dependentscattering ability, a nonmagnetic film 92, and a ferromagnetic film 93were formed on a substrate 90. The film thicknesses of the ferromagneticfilms 91 and 93 and the nonmagnetic film 92 were identical with those inExample 33. An antiferromagnetic film 94 with a thickness of 2 to 50 nmwas formed on the resultant structure, and an exchange bias was appliedto the ferromagnetic film 93. In addition, a hard magnetic film 95having a thickness of 10 to 50 nm and consisting of CoPt or CoNi wasformed on the antiferromagnetic film 94. Electrode terminals 96 werealso formed on the hard magnetic film 95. All of these films were formedin a static magnetic field (in the x direction in FIG. 64).

Subsequently, a magnetic field of 400 to 800 kA/m generated by theantiferromagnetic film 94 was applied in the same direction as thedirection of the exchange bias magnetic field, magnetizing the hardmagnetic film 95 in the x direction. Consequently, a bias magnetic fieldwas applied to the ferromagnetic film 91 in the -x direction due to aleakage magnetic field from the edge portion of the hard magnetic film95, so the magnetization directions of the ferromagnetic films 91 and 93became antiparallel to each other. Although a bias magnetic field fromthe hard magnetic film 95 is also applied to the ferromagnetic film 93,the above antiparallel magnetization state can be realized by settingthe exchange bias force in a way which makes the exchange bias magneticfield from the antiferromagnetic film 94 stronger. Note that the hardmagnetic film 95 and the antiferromagnetic film 94 need not be formed onthe entire surface of the ferromagnetic film 93 but may be formed ononly the edge portions (near the electrode terminals 96) of theferromagnetic film 93.

A ferromagnetic film with magnetism close to soft magnetism is alsousable as the film 95 shown in FIG. 64 in place of the hard magneticfilm. In this case, this ferromagnetic film with magnetism close to softmagnetism must be so stacked as to be applied with the exchange biasfrom the antiferromagnetic film 94. The application of the exchange biasto the ferromagnetic film 95 can lock the magnetization of theferromagnetic film 95 in one direction. Therefore, even if an externalmagnetic field such as a signal magnetic field is applied, a stablestatic coupled magnetic field can be applied to the ferromagnetic film91 in a direction different by 180° from the direction of the exchangebias magnetic field from the antiferromagnetic film 94, which is appliedto the ferromagnetic film 93 when the film is processed into a finepattern that is essential to a magnetoresistance effect. At this point,a bias magnetic field with a desired intensity can be applied to theferromagnetic film 91 by adjusting the film thickness or saturationmagnetization of the ferromagnetic film 95.

It is also possible to apply a desired shunt current operating pointbias by controlling the resistivity or film thickness of theferromagnetic film 95. In this case, it is difficult for theferromagnetic film 95 to have botch of characteristics required to beexchange-coupled with the antiferromagnetic film 94 (that is, to realizeepitaxial growth with the antiferromagnetic film 94, it is desirable touse a crystalline ferromagnetic film, such as an NiFe film, a CoFe film,a CoFeTa film, or a CoFePd film, which has a crystal structure and alattice constant similar to those of the antiferromagnetic film 94), andcharacteristics required for a static coupled bias or an operating pointbias (that is, the resistivity of the above crystalline film is toolow). It is therefore preferable that the ferromagnetic film 95 have atwo-layered structure in which a magnetic film (e.g., NiFe- orCoFe-based ferromagnetic film) for exchange coupling, which is incontact with the antiferromagnetic film 94, and a biasing ferromagneticfilm (e.g., a Co-based amorphous film, a nitride fine crystal film suchas an FeTaN film, or a carbide fine crystal film such as an FeZrC film),are exchange-coupled ferromagnetically in the interface between them.

In the structure shown in FIG. 64, since a sense current from theelectrode terminals 96 is shunted to the hard magnetic film 95, acertain degree of decrease in ΔR/R is unavoidable. This problem can besolved by structures shown in FIGS. 65 to 67.

That is, as shown in FIG. 65, films up to an antiferromagnetic film 94are formed on a substrate 90 as in the structure shown in FIG. 64, andhard magnetic films 95 are then formed near the two sides of theantiferromagnetic film 94. Electrode terminals 96 are formed inside thehard magnetic films 95 with a spacing corresponding to the track width.This consequently makes it possible to prevent a sense current fromflowing into the hard magnetic film 95, preventing the reduction inΔR/R.

As shown in FIG. 66, on the other hand, a hard magnetic film 95 isformed first on a substrate 90, and then a ferromagnetic film 91, anonmagnetic film 92, a ferromagnetic film 93, and an antiferromagneticfilm 94 are formed in sequence on the hard magnetic film 95 via aninsulating film 97. Electrode terminals 96 are also formed on theresultant structure. A static magnetic field is applied during the filmformation, thereby applying a predetermined exchange bias magnetic fieldfrom the antiferromagnetic film 94 to the ferromagnetic film 93. Afterthe film formation, the hard magnetic film 95 is magnetized in the samedirection as the direction of this exchange bias. This method can applythe bias magnetic fields in opposite directions to the ferromagneticfilms 91 and 93 and can also prevent a current from flowing into thehard magnetic film 95. Note that the insulating film 97 has an effect ofpreventing application of an excessive bias magnetic field resultingfrom exchange coupling between the hard magnetic film 95 and theferromagnetic film 91.

In addition, as shown in FIG. 67, a ferromagnetic film 91, a nonmagneticfilm 92, a ferromagnetic film 93, and an antiferromagnetic film 94 areformed in sequence on a substrate 90. Subsequently, the resultantstacked film is formed into a predetermined fine pattern. This finepatterning is performed by ion milling upon forming a mask by using aresist or the like. Thereafter, the remaining mask is used to form hardmagnetic films 95 on the sides of the ferromagnetic film 91 by use of alift-off process. Lastly, the hard magnetic films 95 are magnetized inthe opposite direction of the direction of an exchange bias applied tothe ferromagnetic film 93. This method can also prevent a current fromflowing into the hard magnetic films 95 as well as applying the biasmagnetic fields in opposite directions to the ferromagnetic films 91 and93.

EXAMPLE 35

In the spin valve structure shown in FIG. 63, a 5-nm thick Cuundercoating film containing 1 at % of Cr, a 15-nm thick FeMn film as anantiferromagnetic film 82, a 1-nm thick Ni₈₀ Fe₂₀ film as aferromagnetic film 83a, a 1.5-nm thick Cu film containing 1 at % of Cras a nonmagnetic film 87, a 6-nm thick Ni₈₀ Fe₂₀ film as a ferromagneticfilm 83b, a 2.5-nm thick Cu film as a nonmagnetic film 84, a 6-nm thickNi₈₀ Fe₂₀ film as a ferromagnetic film 85b, a 1.5-nm thick Cu filmcontaining 1 at % of Cr as a nonmagnetic film 87, a 1-nm thick Ni₈₀ Fe₂₀film as a ferromagnetic film 85a, and a 15-nm thick FeMn film as anantiferromagnetic film 82 were formed in sequence on a glass substrate80.

The formation of all these films was performed in a static magneticfield of a permanent magnet by using a double-pole sputtering processwithout breaking a vacuum. Note that this permanent magnet was notconnected integrally with a substrate holder. The film formation wasperformed at a preexhaust pressure of 1×10⁻⁴ Pa or less and an Ar gaspressure of 0.4 Pa. When the formation of the ferromagnetic film 83 wasfinished, the substrate holder was rotated 180° to reverse the directionof the bias magnetic field (approximately 4,000 A/m) of the permanentmagnet 180°. In this manner, a stacked film with a spin valve structurecapable of realizing an antiparallel state of the magnetizations of thetwo ferromagnetic films when the signal magnetic field was 0 wasmanufactured.

The resistance of the resultant stacked film was measured by afour-terminal process. More specifically, a constant current of 1 mA wassupplied to the ferromagnetic films 83 and 85 in the direction of theaxis of easy magnetization, and a voltage across 4 mm was measured bysetting the film width in the direction of the axis of hardmagnetization at 1 mm. The magnetic field was applied to theferromagnetic films 83 and 85 along the axis of hard magnetization byusing a Helmholtz coil. FIG. 68 shows the consequent resistance-magneticfield characteristics.

Referring to FIG. 68, the resistance is plotted by normalizing a valueobtained by a maximum magnetic field (16 kA/m) to 1. when the magneticfield is 0, the resistance shows its maximum value since themagnetization directions of the ferromagnetic films 83 and 85 areantiparallel to each other. When a magnetic field is applied, theresistance decreases abruptly. Especially when the magnetic field is2,000 A/m or more, the resistance shows a substantially constant value.This demonstrates that a resistance change rate of about 3.8% or lesstakes place within the range of a slight magnetic field of 2,000 A/m orless. In addition, almost no hysteresis and almost no noise are found inthe resistance-magnetic field characteristics. That is, the use of thisspin valve type stacked film makes it possible to obtain a magnetic headwhich has a significantly high sensitivity and causes little noise.

Separately, the spin valve type magnetoresistance effect element shownin FIG. 62 was manufactured, and the relationship between the thicknessand the resistance change rate of the nonmagnetic film 84 (Cu) waschecked. The result is shown in Table 5 below. A 5-nm thick NiFe filmwas used as the undercoating film, 8-nm thick NiFe films were used asthe ferromagnetic films 83 and 85, and a 10-nm thick FeMn film was usedas the antiferromagnetic film 82.

                  TABLE 5                                                         ______________________________________                                        Thickness (nm) of                                                                            Resistance change                                              interlayer (Cu)                                                                              rate (%)                                                       ______________________________________                                        1.2            9.1                                                            1.6            5.7                                                            2.2            3.9                                                            3.3            3.0                                                            ______________________________________                                    

As can be seen from Table 5, the resistance change rate increasedabruptly as the Cu thickness decreased, and, when the Cu thickness was1.2 nm, a high resistance change rate of 9% could be obtained. This isso because relatively large antiparallel bias magnetic fields of 50 kA/mwere applied to the ferromagnetic films 83 and 85, and this realized anantiferromagnetic magnetization arrangement even when the thickness ofthe nonmagnetic film 84 was decreased. When the thickness of thenonmagnetic film (Cu) is decreased to less than 2 nm, the antiparallelmagnetization arrangement is broken to decrease the resistance changerate abruptly in conventional spin valve type magnetoresistanceelements. In the present invention, however, the resistance change ratecan be increased largely by applying the bias magnetic fields in theopposite directions to the ferromagnetic films 83 and 85 and decreasingthe thickness of the nonmagnetic film 84.

EXAMPLE 36

A structure in which the number of ferromagnetic films having aspin-dependent scattering ability was increased to three or more will bedescribed.

As shown in FIG. 69, an undercoating film 101 for controlling theorientation of an antiferromagnetic film 102, an antiferromagnetic film102 consisting of, e.g., FeMn, NiO, or PtMn and having a thickness of 5to 50 nm, a ferromagnetic film 103 consisting of, e.g., CoFe, Co, orNiFe and having a thickness of 1 to 20 nm, a nonmagnetic film 104consisting of, e.g., Cu or Au and having a thickness of 1 to 10 nm, aferromagnetic film 105 with a thickness of 1 to 20 nm, a nonmagneticfilm 106 with a thickness of 1 to 10 nm, a ferromagnetic film 107 with athickness of 1 to 20 nm, and an antiferromagnetic film 108 with athickness of 5 to 50 nm were formed on a substrate 100. The filmthicknesses of the ferromagnetic films 103, 105, and 107 may be the sameor different. Electrode terminals 109 were formed on the resultantstructure after a protective film was formed if necessary. The filmformation was performed in a static magnetic field.

Exchange biases were applied from the antiferromagnetic films 102 and108 to the ferromagnetic films 103 and 107, respectively, in onedirection (the x direction in FIG. 69). As a result, a permeabilitybecame high only in the intermediate ferromagnetic film 105 and low inthe ferromagnetic films 103 and 107; that is, magnetization locking wasrealized. This magnetization locking can also be realized by the hardmagnetic film 95 as shown in FIG. 65 rather than the antiferromagneticfilms. Note that it is possible to realize a high resistance change ratein a low magnetic field by using Co or CoFe which has not so good softmagnetism but a high resistance change rate, as the material of theferromagnetic films 103 and 107 in contact with the antiferromagneticfilms 102 and 108, and NiFe which as not so high resistance change ratebut a good soft magnetism, as the material of the intermediateferromagnetic film 105.

With this arrangement, magnetization rotation of the intermediateferromagnetic film 105 occurs easily in a low magnetic field. Inaddition, since the number of interfaces via nonmagnetic layers isincreased to be twice that in a conventional spin valve type stackedfilm, a resistance change rate higher than that of the conventional spinvalve type stacked film can be realized in a low magnetic field.Furthermore, since the ferromagnetic film whose magnetization is rotatedby a signal magnetic field is present in the middle of this stackedfilm, the magnetization of the ferromagnetic film is disturbed onlyslightly by a sense current magnetic field, and this makes stable signaldetection possible. Note that by using the bias process using the hardmagnetic film or the demagnetizing field as explained in Example 34, themagnetization direction of the ferromagnetic films 103 and 107 and themagnetization direction of the ferromagnetic film 105 can be set to beantiparallel to each other when the signal magnetic field is 0.Consequently, a magnetoresistance effect element which has a highersensitivity and causes less noise can be obtained by the various effectsdescribed in Example 33.

EXAMPLE 37

FIG. 70 illustrates a stacked film in which the number of ferromagneticfilms with a spin-dependent scattering ability was increased to four.

Referring to FIG. 70, an antiferromagnetic film 111, four ferromagneticfilms 112, 114, 116, and 118 stacked via nonmagnetic layers 113,115, and117, and another antiferromagnetic film 119 were formed in sequence on asubstrate 100, and electrode terminals 109 were formed on the resultantstructure such that a sense current flowed in the same direction as thatof a signal magnetic field. If necessary, an undercoating film forcontrolling orientation was formed below the antiferromagnetic film 111,and a protective film was formed on the antiferromagnetic film 119. Thematerials and film thicknesses of the individual films were identicalwith those of the structure shown in FIG. 69.

During the formation of at least the ferromagnetic film 112, a staticmagnetic field was applied in the x direction (the track widthwisedirection) in FIG. 70. During the film formation after that film, thedirection of the static magnetic field was reversed 180°, and thismagnetic field was applied during the formation of at least theantiferromagnetic film 119 in the -x direction shown in FIG. 70. Uponapplication of the static magnetic field, magnetization locking wascaused in the x direction in the ferromagnetic film 112 and in the -xdirection in the ferromagnetic film 118 by an exchange bias magneticfield. In this arrangement, a strong demagnetizing field is generated inthe track widthwise direction if the track width is narrow, since thewidth of the ferromagnetic films 112, 114, 116, and 118 is also narrowin that case. This demagnetizing field causes the magnetizationdirections of the intermediate ferromagnetic films 114 and 116 not incontact with any antiferromagnetic film to be antiparallel to themagnetization directions of the ferromagnetic films 112 and 118,respectively. That is, when the signal magnetic field is 0, thedirections of the adjacent magnetizations of these four ferromagneticfilms are antiparallel to each other.

If the demagnetizing field to the intermediate ferromagnetic films 114and 116 is insufficient, it is desirable to supply a sense current inthe y direction in FIG. 70 such that a magnetic field generated by thesense current is applied to the ferromagnetic films 112 and 114 in the-x direction and to the ferromagnetic films 116 and 118 in the xdirection. In this case, by setting the exchange bias magnetic fieldfrom the antiferromagnetic film to be larger than the sense currentmagnetic field, the magnetization directions of the ferromagnetic films112 and 118 can be locked in the direction of the exchange bias from theantiferromagnetic film without being disturbed by the current magneticfield.

With the above arrangement, the individual magnetization directions ofthe four ferromagnetic films can be arranged antiferromagnetically whenthe signal magnetic field is 0. Therefore, the ΔR/R increases with anincrease in the number of interfaces. In addition, since themagnetization of each layer can rotate upon application of a slightsignal magnetic field, a magnetoresistance effect element using a highlysensitive spin-dependent scattering can be realized.

EXAMPLE 38

This example explains a structure in which magnetizations of someferromagnetic films with a spin-dependent scattering ability are lockedand magnetizations of the remaining ferromagnetic films are arranged ina direction different from the direction of a signal magnetic field whenthe signal magnetic field is 0.

FIG. 71 shows a stacked film in which the directions of a sense currentand a signal magnetic field are perpendicular to each other. Referringto FIG. 71, a stacked film of ferromagnetic films 121 and 123 which hada spin-dependent scattering ability and between which a nonmagnetic film122 was interposed, and an antiferromagnetic film 124 were formed insequence on a substrate 120. The materials and film thicknesses of thesefilms were identical with those of the structure shown in FIG. 62. Aftera protective film was formed on the antiferromagnetic film 124 asneeded, electrode terminals 125 were formed.

During the formation of at least the ferromagnetic film 121, a staticmagnetic field was applied in the x direction in FIG. 71. During theformation of at least the antiferromagnetic film 124, on the other hand,the static magnetic field was applied in a direction (the y direction inFIG. 71) which was rotated 90° from the first direction. As a result,the axis of easy magnetization of the ferromagnetic film 121 wasarranged in the x direction, and the magnetization of the ferromagneticfilm 123 was locked in the direction of a signal magnetic field by abias magnetic field from the antiferromagnetic film 124. With thisarrangement, the angle defined between the magnetizations of the twoferromagnetic films is 90° when the magnetic field is 0. when the signalmagnetic field is applied in the direction of magnetization locking ofthe ferromagnetic film 123, the magnetizations of the two ferromagneticfilms form a ferromagnetic arrangement, and this decreases theresistance. When the signal magnetic field is applied in a directiondifferent by 180° from the magnetization locking direction, themagnetizations of the two ferromagnetic films are arrangedantiferromagnetically, thereby increasing the resistance, This makes itunnecessary the use of an operating point bias which is required inconventional magnetoresistance effect elements. In this method, thedynamic range is small because the magnetization of the ferromagneticfilm 121 tends to incline from the x direction to the y direction due tothe ferromagnetic coupling between the ferromagnetic films 121 and 123when the signal magnetic field is 0. That is, a reproduction signal iseasily distorted upon application of a large signal magnetic field. Thisproblem can be avoided by determining the flowing direction of a sensecurrent such that a magnetic field generated by the sense current isapplied in a direction different by 180° from the direction of thisferromagnetic magnetic field in the ferromagnetic film 121, i.e., theferromagnetic field and the current magnetic field cancel each otherout.

In a case wherein a film having an anisotropic magnetoresistance effectis used as the ferromagnetic film 121 or 123, however, if themagnetization M of the ferromagnetic film 121 is inclined to thedirection of the magnetization M of the ferromagnetic film 123 by theferromagnetic coupled magnetic field, an improvement of sensitivity canbe expected since the magnetic anisotropy and the resistance changeresulting from spin-dependent scattering are superposed (because thecurrent direction is the x direction). In practice, the magnetizationdirection of the ferromagnetic film 121 must be adjusted by means of acurrent direction or the like depending on situations where themagnetoresistance effect element is used.

In Example 38, it is necessary to apply longitudinal bias magnetization(a bias magnetic field in the x direction in FIG. 71) required to reduceBarkhausen noise. For this purpose, an antiferromagnetic film asexplained in Example 33 is arranged on the substrate side of theferromagnetic film 121 to obtain exchange coupling between them.Alternatively, as shown in FIG. 72A, a ferromagnetic film 126 with softmagnetism excellent to some extent (in which Hc is smaller than anexchange bias magnetic field H_(UA)) is stacked on the ferromagneticfilm 124. During the stacking of at least this ferromagnetic film 126,the direction of the bias magnetic field during the film formation isrotated about 90° to apply the exchange bias magnetic field from theantiferromagnetic film 124 in the -x direction in FIG. 72A. In thismethod, since the film formed as a spin-dependent scattering unit alsoserves as an undercoating film, an exchange bias can be applied easilyto the ferromagnetic film 126 formed on the antiferromagnetic film 124.Consequently, Barkhausen noise can be reduced since the longitudinalbias magnetic field in the +x direction can be applied to theferromagnetic film 121 by a static coupled magnetic field (ademagnetizing field) generated when the film is processed into a finepattern suitable for a reproducing head.

In the structure shown in FIG. 72A, the bias magnetic field directionbecomes unstable in some cases because the exchange bias directions aredifferent on the two sides of the antiferromagnetic film 124. Thisproblem can be avoided by, as shown in FIG. 72B, separating theantiferromagnetic film 124 into antiferromagnetic films 124a and 124c byforming a very thin interlayer 124b (an fcc-phase film consisting of,e.g., Cu), which weakens magnetic coupling but does not interfere withcrystal growth, in the middle of the antiferromagnetic film 124. Theantiferromagnetic films 124a and 124c are preferably made of materialshaving different N eel points or different blocking temperatures (sincethe direction of the exchange bias magnetic field can be controlled evenby a heat treatment, as explained in Example E1). In addition, nodesired longitudinal bias magnetic field can be applied to theferromagnetic film 121 unless the ferromagnetic film 126 is thick and Bsis high. In this case, the resistivity of the ferromagnetic film 126 ispreferably high because a sense current is shunted to the ferromagneticfilm. More specifically, the use of a Co- or Fe-based amorphous film ora nitride or carbide fine crystal film is desirable. However, a film ofthis kind is difficult to be exchange-coupled with the antiferromagneticfilm consisting of, e.g., FeMn. It is therefore desirable that a verythin ferromagnetic film 126b, which consists of, e.g., NiFe or CoFeTaand is easy to be exchange-coupled, be stacked on a portion in contactwith the antiferromagnetic film 124a, so that a high-resistance,amorphous-like, high-Bs ferromagnetic film 126a is ferromagneticallyexchange-coupled to the ferromagnetic film 126b when stacked on it.

EXAMPLE 39

FIG. 72C illustrates a stacked film in which the directions of a sensecurrent and a signal magnetic field are parallel. This arrangement isidentical with that shown in FIG. 69 except for the flowing direction ofa sense current. Consequently, the longitudinal direction of the filmrotates 90°. Also in this arrangement, the angle defined between themagnetization directions of two ferromagnetic films is 90° when themagnetic field is 0. when the signal magnetic field is applied in thedirection of magnetization locking of a ferromagnetic film 123, theresistance decreases since the magnetizations of the two ferromagneticfilms form a ferromagnetic arrangement. When, in contrast, the signalmagnetic field is applied in a direction different by 180° from themagnetization locking direction, the resistance increases because themagnetizations of the two ferromagnetic films are arrangedantiferromagnetically. Therefore, no operating point bias is necessary.In this arrangement, the direction of a magnetic field generated by asense current equals the direction of the axis of easy magnetization,and this magnetic field has an effect of suppressing Barkhausen noise.

In Example 39, the magnetization of a ferromagnetic film 121 tends topoint in the y direction due to a ferromagnetic coupled magnetic fieldwhich is generated easily from the ferromagnetic film 123. As isexplained in detail in Example 39, this ferromagnetic coupled magneticfield has an effect of superposing an anisotropic magnetoresistanceeffect although the dynamic range of the signal magnetic field isnarrowed. Note that the axis of easy magnetization of the ferromagneticfilm 121 need not exist in the x direction since the current magnetofield is applied to the ferromagnetic film 121.

If the Barkhausen noise reducing effect is unsatisfactory, a strongerBarkhausen noise suppressing magnetic field can be applied by offsettingthe magnetization locking direction of the ferromagnetic film 123 fromthe signal magnetic field direction, since a static coupled magneticfield is generated in the x direction in FIG. 72C.

In this case, the Barkhausen noise suppressing effect is slight when θ(the angle between the magnetization direction of the magnetic film 123and the x direction) >60°, which the operating point bias becomesnecessary in order to obtain a linear signal reproduction when θ<30°.Therefore, it is preferable that the range of the offset of the magneticfilm 123 is from 30° to 60°.

EXAMPLE 40

FIG. 73 shows a stacked film in which the number of ferromagnetic filmshaving a spin-dependent scattering ability is three. FIG. 73 illustratesa case in which the directions of a sense current and a signal magneticfield are perpendicular to each other. An antiferromagnetic film 131, astacked film of ferromagnetic films 132, 134, and 136 which had aspin-dependent scattering ability and between which nonmagnetic films133 and 135 were interposed, and another antiferromagnetic film 137 wereformed in sequence on a substrate 130 in a static magnetic field.Electrode terminals 138 were then formed on the resultant structure.

The direction of the static magnetic field remained the same (the ydirection in FIG. 73) during the formation of at least the ferromagneticfilm 132 and the antiferromagnetic film 137, and was changed to adirection (the x direction in FIG. 73) perpendicular to the firstdirection during the formation of the ferromagnetic film 134. As aresult, the magnetizations of the ferromagnetic films 132 and 136 werelocked in the y direction, whereas the magnetization of theferromagnetic film 134 pointed in a direction close to the x directionas the axis of easy magnetization when the magnetic field was 0 whilemaintaining a high permeability, In this arrangement, therefore, theangle defined between the magnetization directions of the twoferromagnetic films is almost 90° when the magnetic field is 0. When thesignal magnetic field is applied in the direction of magnetizationfixing of the ferromagnetic film 136, the resistance decreases becausethe magnetizations of the two ferromagnetic films form a ferromagneticarrangement. In contrast, when the signal magnetic field is applied in adirection different by 180° from the magnetization locking direction,the resistance increases since the magnetizations of the twoferromagnetic films are arranged antiferromagnetically. This makes anoperating point bias unnecessary. With this arrangement, the sensitivityalso increases because the number of interfaces is doubled.

EXAMPLE 41

The resistance-magnetic field characteristics of a stacked film of amagnetoresistance effect element manufactured according to the method ofExample 38 will be described below.

In the structure shown in FIG. 71, a sapphire C-plane substrate was usedas the substrate 120, a 6-nm thick Co₉₀ Fe₁₀ film having a 5-nm thick Pdundercoating film was used as the ferromagnetic film 121, a 3-nm thickCu film was used as the nonmagnetic film 122, a 4-nm thick Co₉₀ Fe₁₀film was used as the ferromagnetic film 123, and a 15-nm thick FeMn filmwas used as the antiferromagnetic film 124. In addition, a 5-nm thick Pdfilm was formed as a protective film on the resultant structure.

All the films of this stacked film structure were formed by adouble-pole sputtering process while maintaining a vacuum. A staticmagnetic field generated by a permanent magnet was applied during thefilm formation. After the formation of the ferromagnetic film 121, thedirection of this static magnetic field was rotated 90° to form an angleof 90° between the axes of easy magnetization of the ferromagnetic films121 and 123. The sputtering preexhaust pressure was 1×10⁻⁴ Pa or less,and the sputtering pressure was 0.4 Pa.

The resistance-magnetic field characteristics of this stacked film weremeasured in the same manner as in Example 34. FIG. 74 shows theresultant resistance-magnetic field characteristics in the axis of hardmagnetization. Referring to FIG. 74, the resistance is normalizedassuming that a value obtained by a ferromagnetic magnetizationarrangement is 1. As shown in FIG. 74, a highly linear change in theresistance with the magnetic field can be obtained when the magneticfield is 0. This demonstrates that no operating point bias is necessary.

EXAMPLE 42

Example 42 shows a magnetoresistance effect element in whichferromagnetic films or bias antiferromagnetic films were stacked on theuppermost ferromagnetic film under and/or lowermost ferromagnetic filmof a spin-dependent scattering unit constituted by ferromagneticfilm/nonmagnetic film/ferromagnetic film and resulting bias magneticfields were generated almost perpendicular to each other.

FIG. 75 shows a multilayered film formed by stacking a first bias film121a for applying a bias magnetic field, a spin-dependent scatteringunit (constituted by a ferromagnetic film 121, a nonmagnetic film 122,and a ferromagnetic film 123), and a second bias film 124 for applying abias magnetic field. The first bias film 121a consisted of any of a hardferromagnetic film made of, e.g., CoPt, a high-Hk ferromagnetic film(e.g., a CoFeRe film with an Hk of 5 kA/m) having a uniaxial magneticanisotropic magnetic field Hk larger than that of the ferromagnetic filmof the spin-dependent scattering unit, and an antiferromagnetic filmmade of, e.g., NiO. The second bias film 124 consisted of anantiferromagnetic film made of, e.g., FeMn. A bias magnetic fieldgenerated by the first bias film 121a of this multilayered film isapplied mainly to the ferromagnetic film 121 by exchange couplingrunning through the interface of the stacked film. A bias magnetic fieldgenerated by the second bias film 124, on the other hand, is appliedprimarily to the ferromagnetic film 123 by the exchange coupling runningthrough the interface of the stacked film. In this case, the first andsecond bias magnetic fields are so applied as to be nearly perpendicularto each other. In addition, the second bias magnetic field is set tohave a strength (desirably 10 kA/m or more) by which the magnetizationof the ferromagnetic film 123 is essentially kept locked uponapplication of a signal magnetic field. On the other hand, the firstbias magnetic field is allowed to have a strength by which themagnetization of the ferromagnetic film 121 can be rotated by a signalmagnetic field and Barkhausen noise can be suppressed. Morespecifically, it is desirable that the bias magnetic fields of the biasfilm 121a and the ferromagnetic film 121 be of 5 kA/m or less when anantiferromagnetic film is used as the first bias film. When aferromagnetic film is used as the first bias film, the magnetizationdirection of the ferromagnetic film 121a is held in one direction tohave a single domain by some means, thereby integrating theferromagnetic films 121a and 121 through strong exchange coupling. As aresult, the magnetization of the ferromagnetic film 121 can be rotatedin substantially the same manner as that of the ferromagnetic film 121a.Since the ferromagnetic film 121a has a single domain, the ferromagneticfilm 121 also has a single domain, and this makes removal of Barkhausennoise possible. Alternatively, the exchange coupling between theferromagnetic films 121a and 121 may be weakened to 5 kA/m or less (byinserting another layer into the interface). In this case, themagnetization of the film 121 and the film 121a rotates independence.The permeability of the ferromagnetic film 121a, is preferable to reduceand make the magnetization difficult to move. As this permeabilityreducing means, an increase in the Hk, an increase in the coerciveforce, or application of a unidirectional bias magnetic field to theferromagnetic film 121a by some means is usable. To impart a singledomain to the ferromagnetic film 121a, as shown in FIG. 76, theferromagnetic film 121a may be elongated to be longer than the spinvalve unit to stack additional antiferromagnetic films or hard films121b on the edge portions of the ferromagnetic film 121a.

When a magnetoresistance effect element with the above arrangement ismanufactured, the magnetization direction of the ferromagnetic film 123is locked, while that of the ferromagnetic film 121 changes inaccordance with the signal magnetic field. Therefore, like in theexample shown in FIG. 71, a high-sensitivity magnetoresistance effectelement having a high linearity when the signal magnetic field is 0 canbe provided. Note that since it is also possible to remove domain wallsfrom the magnetic film 121 for detecting a signal magnetic field, nooperating point bias is necessary, and this makes high-sensitivity,noise-free signal magnetic field reproduction possible.

It is desirable to set the direction of the axis of easy magnetizationof the ferromagnetic film 121 to be perpendicular to the direction ofthe bias magnetic field especially when a Co-based ferromagnetic filmwith a large magnetic anisotropy is used as the film 121. This makes itpossible to cancel a saturation magnetic field corresponding to theanisotropic magnetic field and the bias magnetic field, thereby largelyreducing the Hs. Consequently, the slope of the saturation magneticfield-resistance characteristics shown in FIG. 71 becomes steep to makesignal magnetic field detection at a high sensitivity possible comparedto a case in which the direction of the bias magnetic field is the sameas the direction of the axis of easy magnetization of the ferromagneticfilm 121. To change the direction of the bias magnetic field from thatof the axis of easy magnetization of the ferromagnetic film, there is amethod in which a magnetic field is applied during formation of theferromagnetic film 121 in a direction different from a direction alongwhich the magnetic field is applied during formation of the bias film121a.

EXAMPLE 43

As shown in FIG. 77, a 20-nm thick Cr undercoating film 141 forcontrolling the orientation of a high-coercive-force film, an 8-nm thickhigh-coercive-force film 142 consisting of, e.g., Co, a 3-nm thickinterlayer 143 consisting of, e.g., Cu, and a 4.6-nm thick ferromagneticfilm 144 consisting of, e.g., NiFe were formed in sequence on a supportsubstrate 140. Electrode terminals 145 were then formed on the resultantstructure, thereby manufacturing a magnetoresistance effect element witha spin valve structure. Note that the film formation was performed byultra-high-vacuum E gun vapor deposition. During the film formation, thesubstrate temperature was set at approximately 100° C., and a vacuumchamber was evacuated to 1×10⁻⁸ 'Pa or less.

The X-ray diffraction pattern of the Co/Cr film was measured when thesubstrate temperature was about 100° C. The result is shown in FIG. 78.As is apparent from FIG. 78, the Cr (200) plane had a high orientationin this film, and the (110) plane had a high orientation in the Co filmhaving this Cr film as an undercoating film. The rocking curvehalf-width of the Co (110) peak was about 3°.

FIG. 79 shows the R-H curve in the direction of the axis of hardmagnetization of the stacked film with the structure ofNiFe/Cu/Co/Cr/substrate shown in FIG. 77 manufactured at a substratetemperature of about 100° C. This R-H curve was formed on the basis ofvalues measured by a four-terminal method by processing the stacked filminto a 2 mm×6 μm pattern through regular resist process and ion milling.During the measurement, the axis of easy magnetization was arranged inthe longitudinal direction of the pattern, and a magnetic field wasapplied in the pattern widthwise direction.

As shown in FIG. 79, when the applied magnetic field was ±80 Oe, theresistance change rate was approximately 6.5%, and the saturationmagnetic field was approximately 3.6 kA/m.

Since the Hc of the high-coercive-force film was about 8 kA/m in thisstructure, no problem arises if a magnetic field from a medium is lessthan 8 kA/m. However, this stacked film is unsuitable for a structure inwhich a head and a medium are set close, i.e., a structure in which amagnetic field from a medium is 8 kA/m or more. Therefore, anotherstacked film with the same structure and film thicknesses as those ofthe stacked film shown in FIG. 77 was formed at a substrate temperatureof about 200° C. in a magnetic field of about 8 kA/m.

The X-ray diffraction pattern of Co/Cr when the substrate temperaturewas approximately 200° C. was almost the same as that shown in FIG. 78.In addition, this stacked film also had a rocking curve half-width ofabout 3° at the Co (110) peak. Furthermore, offset of the hexagonal Caxis was found in the direction of a magnetic field when the film wasmeasured by using a pole figure. Therefore, single-crystal-like Co wasobtained in this stacked film, unlike in the stacked film formed at asubstrate temperature of 100° in the absence of a magnetic field.

FIG. 80 shows the R-H curve in the direction of the axis of hardmagnetization of the stacked film with the same structure as in FIG. 77formed at a substrate temperature of about 200° C. in a magnetic field.Similar to the R-H curve shown in FIG. 79, this R-H curve was alsoformed on the basis of values measured by the four-terminal method byprocessing the stacked film into a 2 mm×6 μm pattern. During themeasurement, the axis of easy magnetization (the direction of the Caxis) was set along the longitudinal direction of the pattern, and amagnetic field was applied in the direction of the pattern width.

As shown in FIG. 80, even when an external magnetic field of ±1.6 kA/mwas applied, the magnetization of the high-coercive-force film wasalmost not moved by the applied magnetic field. In addition, thesaturation magnetic field of the NiFe film could be held at a low valueof approximately 2.8 kA/m, and the resistance change rate wasapproximately 7.5%.

In the stacked film with the above arrangement, the magnetization of thehigh-coercive-force film was stable even with an external magnetic fieldof 1.6 kA/m. Therefore, a pattern was formed in which the axis of easymagnetization of the NiFe film was in the widthwise direction and the Caxis of Co was in substantially the longitudinal direction. Thisarrangement makes an operating point bias unnecessary. In thisarrangement, a magnetic field was applied in the longitudinal directionof the pattern to measure a consequent R-H curve. Note that the patterndimensions were 2 mm×6 μm like in the above structure. The measurementresult is shown in FIG. 81, As can be seen from FIG. 81, a good R-Hcurve free from hysteresis could be obtained, and the Hk showed a lowvalue of about 1.6 kA/m.

Although the Co film was used as the high-coercive-force film in thisexample, a CoNi film and a CoCr film are also usable. In addition, a wfilm can also be used as the undercoating film in place of the Cr film,and other elements may be added to these Cr and W films. Note that thisundercoating film is applicable to an undercoating film of a so-calledhard film throughout the present invention. This allows the C axis toexist in the plane of the hard film (i.e., the C axis is aligned in aparticular direction). When magnetization of the hard film is locked,therefore, magnetization of a ferromagnetic film formed on it can beprevented from being locked.

As a reference, FIG. 82 shows the M-H curves of a stacked film having noundercoating film. FIG. 82 reveals that a leakage magnetic field isgenerated from a vertical component of the magnetization of Co, and thisdegrades the soft magnetic characteristics of an NiFe film. The reasonfor this is assumed that the magnetizations of NiFe and Co are partiallyintegrated.

EXAMPLE 44

As explained in Example 43, since a high-coercive-force film formed at asubstrate temperature of about 200° C. is a single-crystal-like filmwith a low resistance, the mean free path of electrons can be extendedto be much longer than the thickness of the high-coercive-force film.Therefore, as shown in FIG. 83, high-coercive-force films 142 andferromagnetic films 144 were stacked via Cu interlayers 143. Theresistance change rate of this stacked film exhibited a high value ofapproximately 15%. To manufacture a stacked film with such a structure,it is desirable to form an undercoating film in order to control theorientation of the first high-coercive-force film 142. In this example,a Cr film 141 with a thickness of 20 nm was formed as an undercoatingfilm.

An example in which a high-coercive-force film for orientation controlwas used as the bias film in Example 34 will be described below.

EXAMPLE 45

In this example, as shown in FIG. 84, a magnetoresistance effect elementwith a spin valve structure was formed on an orientation controllinghigh-coercive-force film 142 via a magnetic insulating layer 146. Whenthe orientation controlling high-coercive-force film 142 is used in thismanner, the high-coercive-force film 142 and an NiFe film 144 arestatically coupled in a film edge portion, and this makes it possible tolock a domain wall which causes Barkhausen noise at the NiFe film edgeportion. In addition, an influence that the high-coercive-force film hason the NiFe film, e.g., a leakage magnetic field inside the film can beavoided by the use of the orientation controlling high-coercive-forcefilm. Consequently, a high-quality element can be manufactured withoutdeteriorating the soft magnetic characteristics of the NiFe film. Notethat an antiferromagnetic film or the like is also usable as an exchangebias film of this spin valve structure.

As has been described above, the magnetoresistance effect element of thepresent invention can achieve a high resistance change rate andexcellent soft magnetic characteristics regardless of whether theelement comprises a film with a spin valve structure or an artificiallattice film. In addition, the magnetoresistance effect element of thepresent invention makes an operating point bias unnecessary.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices, shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A magnetoresistance effect element comprising:asubstrate; a stacked film formed on said substrate, and a pair of leadsto supply current to said stacked film, said stacked film beingcomprised of a first ferromagnetic film, a second ferromagnetic film anda nonmagnetic film disposed between said first and second ferromagneticfilms wherein said first and second ferromagnetic films are notsubstantially coupled with each other, a direction of magnetization ofsaid first ferromagnetic film is pinned, said second ferromagnetic filmis a field-detecting film, the magnetization of said first ferromagneticfilm does not substantially rotate with lower signal magnetic fieldsthan the magnetization of said second ferromagnetic film does, saidsecond ferromagnetic film comprises a Co alloy having a fcc crystalstructure, and a (111) plane of said stacked film is oriented in adirection perpendicular to a surface of said stacked film, wherein saidnonmagnetic film comprises Cu, Al, Pd, Pt, Rh, Ru, Ir, Au, Ag, a CuPdalloy, a CuPt alloy, a CuAu alloy or a CuNi alloy, wherein said firstferromagnetic film comprises Co, a CoFe-alloy, a CoNi alloy, a NiFealloy, a NiFeCo alloy or Fe₈ N, and wherein said second ferromagneticfilm comprises a CoFe alloy, a CoNi alloy or a NiFeCo alloy.
 2. Anelement according to claim 1, wherein said second ferromagnetic film ismade of Co_(100-x) Fe_(x), x being 5 to
 40. 3. An element according toclaim 1, wherein said first and second ferromagnetic films are made ofCo_(100-x) Fe_(x), x being 5 to
 40. 4. An element according to claim 1,wherein a half-width of a rocking curve is less than 20° at a (111)plane reflection peak of an X-ray diffraction curve of said stackedfilm.
 5. An element according to claim 1, wherein said substrate has asurface roughness of less than 5 nm.
 6. An element according to claim 1,further comprising a first bias film so as to apply a first biasmagnetic field to said first ferromagnetic film, and a second bias filmso as to apply a second bias field to said second ferromagnetic film. 7.An element according to claim 1, further comprising an undercoating filmbetween said substrate and said stacked film, said undercoating filmhaving a fcc crystal structure with a larger lattice constant than thoseof said first and second ferromagnetic films.
 8. An element according toclaim 1, further comprising an undercoating film between said substrateand said stacked film, said undercoating layer comprising a magneticamorphous material.
 9. An element according to claim 2, wherein saidsecond ferromagnetic film further comprises at least one elementselected from the group consisting of Ni, Pd, Al, Cu, Ta, In, B, Nb, Hf,Mo, W, Re, Ru, Rh, Ga, Zr, It, Au, and Ag.
 10. An element according toclaim 6, wherein said stacked film is between said first and second biasfilms.
 11. An element according to claim 6, wherein a direction of saidfirst bias magnetic field is substantially perpendicular to a directionof said second bias magnetic field.
 12. An element according to claim 6,wherein at least one of said first and second bias films comprises anantiferromagnetic film.
 13. An element according to claim 6, wherein atleast one of said first and second bias films comprises a magneticallysoft film.
 14. An element according to claim 7, wherein saidundercoating film has an electric resistivity higher than those of saidfirst and second ferromagnetic films.
 15. An element according to claim7, wherein said undercoating film has a resistivity of 50 μΩ·cm or more.16. An element according to claim 7, wherein said first undercoatinglayer comprises NiFeX in which X is an element selected from the groupconsisting of Rh, Nb, Zr, Hf, Ta, Re, Ir, Pd, Pt, Cu, Mo, W, Ti, Cr, Au,and Ag.
 17. A magnetoresistance effect element comprising:a substrate; astacked film formed on said substrate, and a pair of leads to supplycurrent to said stacked film, said stacked film being comprised of afirst ferromagnetic film, a second ferromagnetic film and a nonmagneticfilm disposed between said first and second ferromagnetic films whereina thickness of said nonmagnetic film is between 0.5 nm and 20 nm, adirection of magnetization of said first ferromagnetic film is pinned,said second ferromagnetic film is a field-detecting film, themagnetization of said first ferromagnetic film does not substantiallyrotate with lower signal magnetic fields than the magnetization of saidsecond ferromagnetic film does, said second ferromagnetic film comprisesa Co alloy having a fcc crystal structure, and a (111) plane of saidstacked film is oriented in a direction perpendicular to a surface ofsaid stacked film, wherein said nonmagnetic film comprises Cu, Al, Pd,Pt, Rh, Ru, Ir, Au, Ag, a CuPd alloy, a CuPt alloy, a CuAu alloy or aCuNi alloy, wherein said first ferromagnetic film comprises Co, a CoFealloy, a CoNi alloy, a NiFe alloy, a NiFeCo alloy or FesN, and whereinsaid second ferromagnetic film comprises a CoFe alloy, a CoNi alloy or aNiFeCo alloy.